For me , the neck profile and shape makes the biggest difference, if I don’t like the feel of it I don’t buy it and I almost know instantly whether it’s for me or not , as far as the sound goes, the choice of strings can make a massive difference ,it took me a long while and a lot of money to find my ideal string, and also a good setup to your preference can make a bass feel totally different , I used to pay for my basses to be setup and I always had to make further adjustments, so I now set them up myself 🙂