I've not had any problems from either, other than some stuff missing from one once - can't remember which it was offhand, but they gladly and quickly made it right. PBL is usually cheaper, but Marco has way deeper stock. I do usually order individual parts rather than rebuild kits anyway - cheaper and I've taken to ordering extra bits to have on hand anyway. No such thing as too many coil stops . If you order enough stuff, you're bound to get a lemon eventually though.

If they seem weak after rebuild, a better question is why. Are the coil stops on tight with no play? Spring washers back on? Is the flipper gap good? Usually weak flippers either mean there's play in the mech somewhere - and it's easy to not get something quite right - or there's friction. Shouldn't really have the latter with new parts, regardless of source...

Also, I've found if the flipper angle is different it can REALLY make the game feel bad sometimes. If you're used to playing something and now the sweet spot for a ramp is a bit different, it feels really bad and you can't quite put your finger on why....almost always a bit off when I've done a rebuild, worst part of it is getting it back where you like them. One of the big selling points for precision flips imo.

Take the clamp out of off, stick a flat head screwdriver in the slot between the two clamp blades, twist and hold to pry it open as someone else suggested. It's not uncommon to need to do this with new or old clamps.