The 100 is a better sailing and much faster boat. The 105 has more interior and one design racing which makes it better for sailing one design and living down below, but that's about it.
That's a pretty bold statement ...? Better sailing is a very subjective term and as to faster ... I have sailed 105s for the better part of a decade and from the times I have seen a J/100 and a J/105 on the same course they have matched pretty close in speed, one can be faster than the other depending on wind conditions and angle of sail. And of course who is driving.
Plus consider ratings (pulled these from ChiMac and Bayview Mac entries) ... they are close, with J/105 rated slightly faster in both cases.
- PHRF: J/100 = 93, J/105 = 87 (lower number faster)
- ORR: J/100 = 0.877, J/105 = 0.89 (higher number faster)
Plus the standard J/100 has one significant disadvantage - no sprit. The J/105 with its sprit will sail deeper than a J/100 without a sprit. Sprit is optional on the J/100 and I have only seen them in pictures.
So better sailing? Maybe, depends on your definition. I do like the tiller but I can have one of those on a 105. Also like the narrow beam and the cockpit layout of the J/100. They are great boats. But for the money the J/105 is a better value, used J/100s are still >$100k last I checked.
But J/100 is "faster", especially much faster? ... no way in hell.