so i got this 89' squier strat and i'm looking for a new bridge for it. the original one is slowly disintegrating. it has a vintage 6-screw.

now i'm faced with a question - authentic fender vintage trem costs 99.99, whereas the one on warmoth is only 44.00

is there any noticeable difference between the two, especially on a lower quality guitar such as mine, will i compromise anything, such as sustain, by going with the cheaper alternative?

It's all about feel
well... I honestly can't think of anything that the $100 fender bridge would give you that a $50 warmoth woudln't. The $50 warmoth is probably worth it. Check out the materials used and compare and contrast them.
Fact: Bears eat beats. Bears beats Battlestar Galactica.
I'd have a look at a Wilkinson Trem, huge upgrade from the Squier trem, and it's given my Squier perfect tuning stability (with locking tuners and a graphite nut).