I believe the fixit sculpt is another version of Magic-sculpt. For the money, it is way cheaper than Milliput, and after
using both, I'd go with the Magic-sculpt. Another filler I'm fond of and use is 30 minute epoxy mixed with micro balloons.
A very light and easy to apply and sand filler I do use the two-part polyester putties, but I don't really have a favorite. Tamiyas
has some neat qualities, but to me they are all mostly the same basic thing.