Well, where the rust is the chrome coating is already gone, so I wouldn't worry about that.
If you've been soldering rust holes shut, you're probably pretty thin all over.
If you wanted to save them, I mean really save them, I'd strip 'em down and repair what I needed to and then send them out for re-chroming. The chromers will make them mirror smooth (well, a good shop will) and then apply the Ni and Cr coatings.
But since it's already started popping through in places, I'm leaning to the side that they are on (or close to) their last legs. The problem with exhaust is that is rusts from the inside out and when you start seeing holes, it's eroded away nearly everywhere.
An advantage to having them re-chromed is chroming is an additive process. Meaning they add metal to the assembly when chroming. they clean and smooth the base material, then lay on a coat of copper, then nickle, and finally chromium. So it will thicken it up ever so slightly. But the real plus is the chrome doesn't see inside or outside of the pipe, it just sees pipe. So it will chrome the interior and the exterior, adding a bit of "meat" and giving more corrosion protection inside where the caustic exhaust gasses pass. Chroming won't save a piece that's too far gone, but it can extend the life of a marginal piece.
If you just want to clean them up, have a go with polishes, rust removers and/or steel wools. But the rust will come back if you leave it bare steel (which is what it is now and why it is rusting). Since the seam is on the underside of the pipes, maybe consider giving the newly "de-rusted" areas a shot of chrome or aluminum paint to help slow down the return of the rust. At least from the outside in.
