Arcs:  13m (Venom or Phantom -- floaty + grunty, but not terrifying and still turns fast) 
Depower Foil:  10m (Speed 4... hand's down my favorite depower foil on the planet... tons of range.)
Fixed Bridle:  3m (I love my old Beamer III and my Hornet 2... flies in anything and fun as hell to this day)
LEI/On Water:  10m for LEIs, but I'd really REALLY like to have a go at my 14m on water.  It's just so... stable and predictable, but lifty with tons
of grunt.  I've just never really had the right conditions, but I really look forward to it (it's a 2012 SS Rally, in case you're curious).  As it is,
though, my go-to kite for like the last year has been the 10m size.  I recently replaced a 2011 Rally in that size with a 2016 Wave SST.  And yeah,
I'm pretty pumped 
 
As for least favorite sizes:
Arcs: 19m Venom (I had to throw away those pants)
Depower Foil:  15m (bowtie machine here in CO)
Fixed Bridle: 5m (blegh)
LEI/On Water: 12m (I just always feel like I'm either under- or over-powered)
All that being said, I'm a total water noob, so I expect this to change significantly by next year 
