I've looked at the numbers of both 210 and 115 cabs, for both Epi and EBS and yes, there's very little difference in therms of frequencies, responses and other things... fine the speaker is larger and the 'box' is differently constructed, but the differences on the paper are not great. I have tested recently a Hartke rig, 4x10 on it's own and then with a 1x15 + 4x10 and I could actually hear the difference in the low end, so I'm not sure now if I was imagining that or if it does make a difference.
I certainly don't want to invest in a 115 and then find out that a) it makes no difference and no one else wants it, so resell value is zilch!
Grrrr... 410 is just too big to go in and out of doors and in and out of the car... I'll have to try somewhere 2x210s and see how that feels!
Generally though, EBS Neoline cabs or stick with Epifani?