Though I went from VTL 250's to Atma-Sphere MA-1 MkIII's, it wasn't because I thought the VTL's were rolled off or that they had any other serious flaws for that matter. I just decided it was time for a change and wanted to try something different.
Actually, I thoroughly enjoyed the VTL's for over six years, they were trouble free and I could happily go back to them. I'm sure my friend who went from the 450's to the VAC Phi 300.1's would say the same thing.
On the other hand, both the 250's and 450's are outclassed when compared to either the MA-1's or the VAC's as they well should be considering the large price differences.