Jim,
I will try to help you "X-ray" the problem (how many projections, by the way?)
I have just bought an XV 3080, because my main concern was sound quality and I was reassured on this forum that it was the same as the 5080; I didn't go for the 5080 because it claims it can load samples via SCSI but it doesn't yet (and I don't like buying promises); so I think that Roland is somehow losing the train here and this makes the difference between a commercial success and a failure. Sound-wise, I think that both have terrific sounds, better than Korg (try to switch the effects off on a Trinity/Triton and hear the difference). I haven't ever used an arpeggiator, so I cannot comment about it. All I can say is that the XV is so good (even without expansions), that I hardly need anything else. Sounds I like most: electric pianos (terrific), drums, basses, strings, choirs, woodwinds (need some tweaking, though). Sound I like least: acoustic piano (nothing beats a dedicated digital piano here).
So, I hope you're closer to making your diagnosis now; however, you can always ask for a second opinion (even to me).