I dunno the Epi 310, but I regularly practice at a place that has a pair of Epi 210 (NYC not UL) in one room and pairs of Epi 410s in some other rooms. And I own a Schroeder 1212.
My highly-non-scientific never-done-a-direct-comparison-in-same-room-with-same-bass-and-head overview:
* both cabs are pretty efficient
* both cabs will take a lot of power
* both cabs get stupid loud
* both cabs have pretty nice high end. These are not crappy tweeters.
* both cabs go pretty deep. No complaints on the low E (I don't do fivers).
* the epi 210 (in pairs) or 410 is MAYBE smoother overall.
* the epi has more of a fuzzy textural midrange, if you know what
I mean. Not harsh at all, just a nice distinctive character that the
Schroeder doesn't have.
* when playing the epi cabs with an aggie preamp, I tended to leave the preamp flat, maybe boost the highs a bit for my passive bass.
* With my Clarus amp at home through the Schroeder, I tend to cut the lows and boost the mids a bit to get more of the presence I like out of it. Might not be necessary with the 1210, which I think has a bit more in the upper mids; but I bought the 1212 to maximize my available low end and I don't regret that - less work for the amp!
* the schroeder 1212 is maybe more boxy-sounding, with more oomph in the midbass. It's loudest in the upper lows / low mids. It's very tight and punchy, yet there's a distinct overtone somewhere in the mids that's part of its character - not really a ringing resonance, but a noticeable voice that's hard to describe... if were any stronger I'd accuse the cab of being boomy in the mids, but as it is, I'd more say that it's nice and warm and not too sterile.
* the schroeder might be a better choice for a slightly more "classic" sound, but it's still pretty "modern". E.g. turn off the tweeter for some serious soul or reggae thump. But even with the tweeter cranked, it is not a bright cab.
* I am guessing that with tweeters cranked, the epi will get considerably brighter than the schroeder will.
* I have a strong gut feeling that if I were able to properly A/B them, the
differences would be immediately obvious.
* I could be happy in a long-term relationship with either one
* the epi costs almost twice as much ... it's up in whappo junior territory
* I bet one of each would sound freakin' awesome