There are so many differences between E+ and vq3 i don't even know where to begin. Weapon jumps, insanely powerful weapons, no item pickup, and on plus, physics. E+ and vq3 are two different worlds in terms of gameplay.

Now to answer the other questions: vq3 is more popular, as it's all people playing cpma vq3 and osp, also the ruleset is the main platform on big tournaments. How do you play vq3? Go and see, lol. ;p Skillwise, i'd say vq3 has a much steeper learning curve, and demands more from the players. Also the people who play vq3 tend to be better than your average E+'ser. All the weapon jumps you practiced on E+ will be useless in vq3, if you play plus.cfg, than you can forget about rail, it's not insta, and is used as a support weapon. Also, if all you ever played is E+, than your ground movement will probably be crippled, and ground movement is very important in vq3. I guess E+ and vq3 clans could play vs each other... but how would that match look like, anyway? They would destroy the other in their "home" environment, so no point in doing something like this (unless it would be like mouz vs dpr or something, hahahah).

e+ = baseq3+more
nothing less nothing more, there aint a reason to use original baseq3 anymore.

Well, you have to understand the difference between terms. What you're talking about is vq3, which is the ruleset - weapon damages, movement physics, switch time, and so on. baseq3 is plain Quake 3, without any mods. People don't play baseq3 anymore, because they play the vq3 ruleset on mods like OSP or CPMA, which, basically, takes the vq3 ruleset and puts it in an environment that gives additional configuration features for the client (enemymodels, custom huds, other crosshairs etc etc).

would the 'unlagged' mod count as baseq3 ? just curious the server is called gin or something