Well, he is the most technical player of all three, most varied in technique, and has the biggest feel regarding his solos.
First, his solos are composed, they aren't improvised. While Dave and Janick, for most of the time, improvise solos on rehersal, and then pick up the best one, Adrian composes them. That's why they have an excellent relation to the chord structure in the background, everything seems perfect.
And also, his solos seem to revolve around the vocal melodies. That's a big plus too, because the vocals set the real melody of the song sometimes.
He plays in different scales. Dave and Janick use minor petatonic scale most of the time.
But the key to H's playing...he knows a lot of different techiniques, and he knows when to use them. He has solos full of fancy tappings, divebombs etc...but still those solos sound like an essential music part of the song, a music part, not somekind of filler.
For instance, the Wicker Man solo, first goes the blues lick, then tapping, then classical style, then shredding. And it's all combined perfectly to match the background musical structure, combined perfectly to match song's mood. And it even goes better...everything is highly melodic, filled with that unique Adrian Smith feel.
He is the fastest among Maiden's axe army, altrough he doesn't play fast all the time. He plays fast when he thinks that's needed. For instance, scaling riff part from CSIT solo, convolution tapping part from SOM solo, or the convolution scale parts from OTGDY or NML solos. It may not sound fast like Dave's fast bluesy legato or Janick's shredding, but, for instance convolution tapping requires perfect coordination of both hands, every note needs to be picked precisely, while Dave's legato requires fast work by right hand, and picking hand just gives accent to each string/note in the sequence. Janick's shredding requires picking hand to shred the wire at 2x tempo of the track. Both of latter techniques are
a lot easier than H's technique.
Just look at CSIT solo...in technical terms, first goes ordinary scale variation, full of melody and artificial harmonics, then downrun followed by a big scalling riff which ends by convolution tapping, then we have two-hand tapping followed by bluesy downward scale run, then a divebomb followed by two-hand tapping and whammy bar usage at the same time.
If you passed on this explanation to someone that didn't hear CSIT, he'll think that solo sounds like some Malmsteen-type guitar show-off. Heh, in reality, CSIT solo is the perfectly composed piece of music for itself, yet full of virtuoso guitar playing, and yet, in every moment, it relates perfectly with the background structure and the main song theme.
I won't even mention his atmospheric solos, alike SIASL or Prodigial Son. Sends shivers down my spine each time i hear them.
Regarding his evolution as a guitarist, at Killers he mainly played melodic parts, while Murray was in charge of faster, legato stuff to brush up the pace. At TNOTB, POM and Powerslave, he started mixing his melodic parts with faster-paced techniques, which culminated on SIT, the best work of his life, ultra-fast paced solos full of techniques, yet retaining the melody. On SSOASS, he cutted the pacing parts a bit to the favor of melodic and atmospheric stuff.
ASAP brought us sound of the '80s, a lot of squeals, but still melody based. It's pity that he didn't proceed with the SIT-type of soloing. Psycho Motel showed that he can both play in different keys and in different rhythms.
Bruce Dickinson era...well, again, playing from different scales (and in different tunings), and at this time, he started using arpeggios for the large portion of his playing. Note : the Man Of Sorrows solo, especially the clean-part at the end of it. The man managed to combine several arpeggios at once, and still there's a melody passing in between. The SIASL-type of melody...
Reunion era showed that H, by combining all techniques he can play (and those are many!), can be really refreshing compared to Dave and Jan who started to lose their ideas. Reunion albums weren't exciting in the terms of H's soloing like SIT was, but again he combines different stuff in one solo to compose a great final product. Wicker Man, No More Lies, Different World, Paschendale, Lord Of Light, BTATS...list goes on.
In essence, Dave and Janick rely on couple of techniques, and they repeat themselves a lot. H does that in a negligible extent, the only straight repeat of his is the OOTS solo, there's a same part of singlehand tapping like in the Wicker Man solo. Yet again, the pace is a lot slower, and both in OOTS and WM that part fits in perfectly.
For the end of this essay, i'll quote a former statement from H's wikipedia entry : "Nobody sounds like Adrian Smith, and that's priceless."
You say $2300 is below average for a Lado?
Well, the standard price is around $2500-2600. It also depends on pickups you want there, and i think you also have a option between Schaller's Floyd Rose and original Floyd Rose.
All those Fenders/Jacksons look the same
Fender Stratocaster is a brand itself. For instance, those custom Jackson strats that both Adrian and Dave used, have licensed Fender headstock. Jackson needed a licence to build the same shape head like the original strat.
And Jacksons do not look all the same
Check out Warrior, Kings V, Randy Rhoads...
The thing is, there's a common name for all those Jackson, Ibanez, ESP, etc. strat-alikes. Superstrats. In early '80s, best guitarists felt crippled with the current guitar market. Thick fretboards, low frets, 22 frets only, non-locking tremolo systems, etc...Then, guys like Vai ordered their custom models from the companies above, stratocaster type of guitar, customized for fast playing.
In essence, those guitars are called superstrats. They have a familiar strat shape, but the guitars are made for high-performance.
I have a superstrat myself, an Ibanez RG. The body is of strat shape, yet it's a bit more pointy, to add to the feel. The fretboard features 24 jumbo frets, and it's probably 1.5 times thinner than "ordinary guitar". The action (space between the strings and the fretboard), is as low as it gets. You know, for metal soloing, you'll do better if you have low action. Still, you can't just tweak the tremolo on the ordinary guitar to achieve low action, because strings will start bouncing off the frets and pickup holders when you start hitting the upper fret notes. Guitar needs to be crafted to support such low action.
Which brings me back to Lado Earth, i've heard a guy say, that guitar has a such low action, and it's crafted in such a manner, if you had 30 frets on it, you'd still be able to play at 30th fret without any bouncing and stuff.
H said he paid like $200 for his Les Paul Gold Top when he got it in like...1974
Well, first, $200 worthed a lot more in 1974 than it does nowadays, and in 1974, Les Paul was something like a mainstream guitar. Nowadays, Les Pauls are more of a vintage stuff, even if they were produced out of the factory this year.
I think they need to follow the studio recordings pretty close when they're playing the songs live. That's just me. H does that almost perfectly.
There's nothing wring with that. I like the shape of the guitar. All those Fenders/Jacksons look the same. I guess that's why I get confused a lot 
