I've been going through a whole bunch of ENB mods (without actually installing them to keep my installation clean) and I've pretty much narrowed it down to two options:

1) http://skyrim.nexusmods.com/mods/15105
2) http://skyrim.nexusmods.com/mods/11318

I like what I see in screenshots from these and they both appear to be updated frequently. I suppose it's a lot about personal preference, but it wouldn't hurt to hear other people's opinions.

So if you're using an ENB mod; which one did you choose and why? And if you've used a different one before, why did you change to your current one?

I use Sharpshooters, no performance loss and it looks great. Forests seem more dense, shadows are great, dungeons are dark and "scary" like I like them. The godrays are cool too. I have never tried Superb's enb so I can't voice my opinion on it.

But I will probably use sharpshooters for the rest of my life in this game.

My suggestion would be to not just go by the screenshots or even other people's advice. Those screenshots might have been taken with a setup that includes other mods that affect visuals, you might be biased by a particularly well-shot screenshot, etc. Even other people will be running mods you don't know about, and that might affect their advice.

Just download them both, go into your game, find a nice scenic shot and save your game at that spot. Then install and activate mod A, start the game and see how it looks. Then exit, turn off mod A, install and activate mod B, start Skyrim and load that same save point. Look at the same view with the different ENB mod working.

Hell, take a screenshot once with Vanilla, once with mod A, and once with mod B. Having identical shots except with different ENB mods in place can really highlight the differences between Vanilla and various mods. It's more work, but it's really the only way to judge between the mods.

This is another point; most of the people commenting will at best have tried one of the two ENBs and not the other. Few people will happen to have tried the same two mods you're trying to choose between.

I'm also still looking for the perfect ENB.

Things I want an ENB to have:
- Support for the Realistic Lighting mod so nights and dungeons are realistically dark
- Accurate (Bokeh) Depth of Field

So far I've tested 2 mods with these:
- Superb ENB-RL
- ENB Real Life Vision - A Photorealistic ENB

Overall I'd say that Superb ENB is better out of the box (without any tweaking). Neither of the mentioned ENBs is perfect in my opinion though so currently I'm trying to combine the best from both.