I only have experience of one of each so not a great sample size but here are my thoughts.
The rehab was the first house I got and I was lucky that the shell is extremely well made and is very solid. It is challenging in places though and I find myself wishing parts weren't already glued on.
It wasn't really until I got the kit (a sugarplum so one of the simple ones) that I really realised how much easier decorating a kit was. It's so nice to be able to plan properly!
However, I do think overall at the moment I am getting more satisfaction and enjoying the rehab more. Feels more unique as it's a house I haven't seen anywhere else.