I would say that people who tried many slot providers and many slot games from those providers have their favorite ones! To do that you really need to be a slot lover, because there're many providers and many of them have a nice selection of slot games!
I say that because I love Betsoft! You name the Betsoft slot and I probably played it... I had crazy big wins with Greedy Goblins, Charms & Clovers, Tipsy Tourist.... and many others! The intro song from Vegas is still in my head from time to time! But it's just Betsoft, how to not love Pragmatic, NoLimit, Relax, Play'n'go... awesome slot providers with awesome slots!
And after all that I started playing Creative Gaming at BC.games! It's not cheap to play Creative Gaming slots, that's for sure! Usually with $1 minimal bet, and some slots with $3-$4 min bet! From the ones I tried just one had a $0.76 min bet! And it's not so easy to win some bonus rounds (like always with all slots), but I had some crazy nice wins from normal spins! And I am starting to like it more and more! When I have a nice balance for sure I will try some spins on Creative Gaming slots!
You're right. Everyone has their own favorite slot and provider and that's because every slot is unique in itself.
Players who want to win big but don't care about winning often will always prefer games from providers like No Limit Gaming while players who want to win more often even if the wins are small they will love slots from Pragmatic Play. It all comes down to what type of slots you want to play. I play money train 2 a lot and I hardly love any other slot from that provider but Money Train 2 is just on another level.