Yea from what I've read, 4.0 is the easiest. I'd probably go with learning to play that.
Yeah, I think 4.0 is easier (And they're still making the books...)
Anyway, I play 3.5 because that was what was out when I started. The two are VERY different games, however. 3.5 is a more classic style whereas 4.0 changed a whole lot. 4.0 was also the first version to come out after the original creators died.
3.5:
A large number of starting classes
Even more "Prestige" classes that can be gained later on
Free multiclassing
Classic spell system (Spellbooks, spells per day, etc.)
Special actions (Bull rush, feint, trip, etc.)
Unique and important feats
Books now out of print. Can only be bought at specialty stores or online
No level cap (I've made a level 1000 wizard once)
Classic races
4.0:
Even more starting classes
"Paragon" classes that you must choose from when you reach... 11 I think.
Either you take a multiclass feat to gain a couple abilities or you make a full hybrid class which is half and half.
"Power" system. Integrates at will, encounter, and daily powers. These encompass everything from fireballs, to powerful thrusts, to holy bursts of light. All classes use powers and they are what really determines how your character acts in combat.
Feats seem kind of cookie-cutter, providing passive numeric bonuses
Books can be found at any bookstore and are still being made
Cap of 30
Unorthodox, or less used races (eladrin, dragonborn, etc.)
I personally prefer 3.5 and that's what my players play. It may also have something to do with my stack of ~25 books, costing upwards of 35$ each.