I've been using SkyRe's combat module for a good while now. I consider it "essential" to a certain point. I love how NPCs get more aggressive and dish out higher damage.

I hear Ultimate Combat is pretty much SkyRe combat except better (in some way). Is this true?

Depends what you want from your combat experience. AFAIK you can use both together but you need to turn off Weapon Swing Cost in UC's MCM menu. You can read up on a reasonably comprehensive breakdown for each in my Combat Mods Guide (link in my sig).

You should also consider adding in ASIS (also summarized in my guide) - there is a SkyRe/ASIS .ini file so both mods will play nicely together.

I would recommend you read the readmes as well just in case anything has changed since I wrote the guide.

Hope that helps...