I've only used the BC loader, there may be better ones out there.
I find they work fine, but you need to pay attention. If it's not feeding or it's jamming, turn the dial back wards a bit. It will usually fix it and the rest feed in.
No matter if I use the loader or hand load the magazines, sometimes you get jams in the rifle. I find it is magazine specific as I have about 8 25 round BC mags and some are infallible while others will cause 2-3 jams per mag, which is resolved by turning the rifle sideways, opening the action, letting the spent case and the loaded round that jams fall out, and thenm continuing on. 70% of the time the loaded round that is ejected is fine to load again, about 30% get mangled.
To me, it's not a big deal, but YMMV