Fox3, old fella. Yeah, well. SA is God, without a doubt, no matter what you fly. And that doesn't mean having all the information in the world, it means having what you need. If we're comparing F-15 with F-3, we need to put aside the obvious differences. Well, not all of them.
I would say this, the F-15 with the kit it carries, radar, data link and defensive aids, along with energy manoeuvrability, is very well placed even in complex environments. But the workload could be an issue. The F-3, in its later days, was blessed with great kit and similarly excellent long range SA.
Now, the question is this. Are we talking post-merge? I think that's the intent of the OP. If we are, the idea is obviously not to have to go there; it's a dangerous place. Hence Phoenix, AMRAAM, etc. but once you get there, airframe performance and ease of targeting become the big factor (including high off boresite aiming). Then, I'd rather be in an F-15 than anything else. No doubt (just taking the types mentioned here).
****ty night over the North Sea trying to work with the Navy with ECM, give me the F-3 and a good Nav.
Is that an answer? Probably not. But it all comes Down to the fact that there are so many scenarios.
Dare I say, "horses for courses."