Conventional question

[numbskull]

A levelwind is going to cost you 10-15 yards. If you plug it is worth it everywhere but the canal. For eels, probably not. The calcutta TE is a very powerful reel....just don't get it wet.

All conventionals without a levelwind will cast an eel about the same distance, the issue becomes how much help you need controlling them.
The smaller reels have better ergonomics which make them easier to cast, but the gears/drags/line capacity may not be up to the size fish you are probably looking for with an eel, particularly in current.

I don't own one, but the 525 Penn mag is supposedly a good casting reel with plenty of guts and some refinements. I like Newells, but that is with mono, with braid each mistake is a disaster. You can slow them with thick oil.

The rod is probably more important than the reel and the opposite of what you would expect. Unless you are throwing only aerodynamic stuff, stay away from fast blanks with conventional reels. They unload too violently and make the reel hard to control so you thumb more and lose distance.

[Nebe]

level winds costing you distance is a farse if you have to tame a non level wind.. I can cast very far with my abu chrome 6500 cs

[Justfishin']

Whenever I fish eels (or bait for that matter) I use a conv. most of the time, for the same reason as piemma: like to free spool a little. I don't have any levelwind casting reels, so I can't compare them.
I fish a 525 Mag a lot, but also still use my 980 Mag in heavier water on a glass-that's right glass - 11 ft Fenglass rod. Use a 970 Mag when on a boat.
The 525 casts a freaking mile, but I also doubled up on the magnets to slow it down and stop the end of the cast backlash. But the reel is not the most solid, lotsa graphite and stamped parts. I'd like to try out an Avet when I meet up with someone who has one.
980 Mag is the best "weight" caster for me- you can really hump heavy bucktails, bait and big eels with one and keep the cast under control. Too bad they stopped making them.