Bruce, welcome to the Forum and the wonderful world of leatherworking...
I currently use three different types of SK blades, a 3/8" straight, 1/4" straight, and a 1/4" angled. For larger designs that do not have a lot of tight turns I use the 3/8" straight blade, for smaller areas I use the 1/4" straight, and for very tight designs with a lot of sharp turns I use the 1/4" angled.
Some of the more proficient carvers can use the 3/8" straight blade with ease for almost all carving, I am not one of them... Since my eyesight is not quite as good as it once was, I find the 1/4" straight blade gives me better vision of my cuts --- for really tight designs the 1/4" angled blade is invaluable, at least for me...