Honestly, you are talking two different guitars here. Both are equally useful, and yes the tremolo systems are completely different. If you don't mind the maitenance of the Ibanez, I feel those are great systems and while they take a little getting used too; they are really great for whammy bar use and for staying in tune. Changing strings and some extended work are involved, but if you do it right it is well worth it.

The strat will come in handy for other things, but in a metal context I don't feel that is a good choice (assuming you are using all single coils.) If you are looking for diversity, I would go with the Ibanez for the time being, and perhaps work to own both if you are able to really make yourself diverse. Good luck and let me know if you have any more questions.