Comparison needed : UltraVerve vs BAT VK 31SE

Can someone with any experience list the difference(s) between these two preamps ? Is the BAT considered an upgrade considering the deHavilland is an overachiever ? Can you describe the sound of the BAT ? Thanks in advance.
Hard to describe the sound of the BAT. I find it to be transparent, musical and reveling.
Never heard the UltraVerve.