A
Ajd3530
, welcome! If I recall correctly, the 38 and 48 have the same handle, just flipped so that the 38 has the blade coming off of the wide end and the 48 has the blade coming off of the narrow end. The 48 will be the most similar to the shape of a slimline trapper. I quite like the 48, but I don't have a 38 to compare. The 15 is a fair bit shorter than the 48 but also a bit wider.
Here's a 48 with a TC barlow, which is also on the 15 frame, so the handle is the same size and shape even though it has a longer bolster and the blade is different.