go for a Sub37, worth the extra cash and will keep its value better. IMO 2 octave keyboard of the SubPhatty is too restrictive. Oscillators on the 37 are supposed to be more stable.
I had a Little Phatty for a few years and really enjoyed owning it, and exploring [i]sound[/i]. Ultimately sold it, as I could get close enough via Arturia's minimoog emulation going into a Moogerfooger analogue filter and needed the space / cash :-)