Is there any real reason to level up Warp/Exit?

I mean, since those spells work "directly", I can´t think of any actual way for them to develop.
The only possibility that comes into mind would be losing less HP while casting it, and I think that makes sense, since that´d mean you won´t lose any HP at all at its highest level.
But I don´t really know, do you have any ideas?

When you cast those spells in combat, they remove enemies from existence. Leveling them up means a higher rate of success.

But otherwise save the MP

what the difference between them in battle?

They do the same thing in battle.

I've found that Warp (The black hole one, I think) seems to be more acurate, when used in battle. Warp, on the field, teleports you back a number of floors equal to the level. E.G, a level 11 Warp spell will take you back 11 floors. Exit does not seem to have any added effect from levelling up, other than costing more MP, and slightly increased Accuracy in battle. Once you level up Warp to, say level 8, you'll never need to use Exit again, as no dungeon is more than 16 floors. A Level 16 Warp spell is basically a Level 16 Exit without the HP Drain, and it's also more accurate.

This topic is for Dawn of Souls im guessing, as Warp and Exit are known as Banish and Warp in Origins. I'm not sure about the originals, you didn't say, Peter. Be a bit more clear next time, okay?

Hope this info helps.

Personally I prefer to be able to Warp up one level at a time, otherwise it's like forcing you to cast the same spell in one go several times. Also, Warp is infact more accurate. Memory doesn't serve me too well, but I believe also that Warp is Black Magic and Exit is White.