There is one "pro" of the HST that I didn't see mentioned yet.  
It is the easiest for hooking up attachments.  There is nothing like being able to go 1/4" back or forward.  My gear tractor has a 50% underdrive/overdrive and in super low, it is still a pain to go back slow and stop on the exact spot.  This may not apply if the attachments are light, but a 1200# cutter or 950# box blade is no fun to move around into position!
Also, the ability to drive into a pile of dirt, slow down without loosing traction and power the bucket full is priceless.   I can move about 25% more dirt in the same time with a 10 cubic foot bucket on my HST tractor than on my gear tractor with a 20 cubic foot bucket.    
jb