Yes the omega-types all present a spherical head-stage; the L700 do not. I listen to a lot of rock and the L700 serves this very well - its unique staging presentation is part of its charm, but not its ONLY charm in comparison to the omega types. I really like the L700 a lot; always have. It maxes out on a BHSE or this HEV90 clone, but also does well on a KGST. Seems to love tubes. The Mk 2 version was a good revision that makes the L700 even better
As far as efficiency - it seems like reports on this ES-1a have been varied. Perhaps this was affected by early pad swapping? Here, with the current stock pads, I find its efficiency to be nearly the same as 007 Mk I - i.e. not very efficient. It's less efficient than the 009, and much less than L700! The HEV90 tube amp audibly struggles to retain grip over the omega types at higher volumes, but does beautifully with L700. It sounds excellent with ES-1a, but you're limited in the volume you can push here before SQ degrades. The 500V IXYS KGSShv provides excellent drive and grip over everything, but is not the best tonal match for 009 and L700.