If it was to be dual boxed, I would say SE. But if it's to be a real player, I might lean towards EE.
SEs have been nerfed up the wazoo, so they are rarely played live anymore. EEs are more capable healers than SE, have faster cast speed, better mp regen speed and better mp regen skills than SEs do. They also have trance, PR and 2nd highest rez in the game.
The big bonus to having an SE (and it is a BIG bonus, don't get me wrong!) is Empower. This is the most important buff for a nuker to have. However, the SH is the strongest nuker and is going to be the most capable of xping w/o empower. I've done the SH/EE duo w/o empower and it does take the SH longer to kill the mob, but it's still non-stop xp because we never run out of mp.
In most pvp situations, I'd say the EE would be the best. The SE just can't heal fast enough to really be of much use.
Just a little tip: One way of getting empower w/o using scrolls is to have an SE w/ emp 3 on the same account as the EE. I am able to log my EE out, emp my sps (or whoever I'm partying with) and log my EE back in, all in about 20-30 seconds. It's really a minor interruption that makes a huge difference in leveling speed. I don't know if this would be feasible for you though, just a thought. :p
Yeah, EE. Clarity, ShockResist, both sheild buffs, dark magic resist. And EE has a few more buffs than SE :) Also, you got better Rez. If you hunt where they drop empower herbs, you should kill fast enought to always have one. EE can assist nuking undead. Go EE :)
SH doesn't need Men, you have passive mp regen, you are the only nuker with mp control, and you have mdef passives,you have boost mp passives and robes +you'll be killing so fast that your def won't matter ad your hp/cp is boosted to cover that, and you can carry more bsps with +con and you shoot harder and faster
If the character will be played live -> EE.
And about empower.. well, a lvl 25 SE box for empower 1 (big enough m.att increase) is easy to make if you don't have scrolls of emp at your disposal.
Be cheap and don't waste precious AA on +4CON -4 STR please, you dont need STR anyways - you nuke stuff. Buy a +4 CON -5 STR dye from the shops in town. And your weight limit goes up from 62 100 to 69 690 which equals a whole lot more shot.
Same goes for the Dex Tat, but you'll get more mileage out of +4 CON than +4DEX with the boost in HPs you dont have to go down that far when CDLing in places.
For example - a clannie of mine CDL at the HS tents with pretty much 0 HPs and he is CDL ing on the new IoP at 900-1K with the same resusults. And he can take 1 hit before he dies and no hits at the HS tents. And with the new spell failures, your going to need to take some hits.