Best Prefix Enchantment

So I have a Water Cylinder that I'm planning to make my main weapon, I shelled out a lot of money to get it because it has the Fresh Suffix, which is usually only for Tower Cylinders, so that already gives it a huge boost. But, I'm not sure which prefix enchantment I should go for.

I'm trying to be a balanced alchemist who ranks all the skills so I don't know if I should go for Moist and get the water Upgrade, or go for Synergy, that nets slightly less water damage but improved fire damage. I could quite easily get either of these scrolls. Or is there some other prefix that might be better?

It's important to note that I don't care about personalization and 10x Repair Cost is already in effect from the Refreshing enchantment.

Well, the question arises, how long have you been doing alchemy? Do you know for sure that you definitely do not or will not later prefer one water over fire or vice versa? Otherwise the answer is evident.