The title says it all,I kinda say that it is worth getting to 100 bronze/silver because you get Cr no matter what.But since,I'm not good at DTs and get t25/t50 I'm kinda like "Nahh,I can't be bothered to get to 100".And If anyone got to 100 just post what Cr you got.
If you can get to 100 bronze isn't very likely whatever you land, no matter how bad, is going to be worth more than spinning them one by one. I got a Kreen Cr once spinning them one by one, but then I dumped about 50 in afterwards and nothing came off it. Random bronze stuff just isn't worth it. Random silver stuff CAN be ok, but then again, landing a mid-range Cr is very, very likely to be worth more.
So if you can get a 100 of either it's kinda always better to.