I appreciate the simplicity of the design without a button, as it reduces the likelihood of problems. I utilize a clip-on loader for my VQ 10/22 mags, which functions flawlessly, clip it on the mag, push down, load the round, release, repeat. (KISS)
For 22LR mags, if the spring pressure is not too much, prefer the thumb button to assist in loading.
I prefer a top loader if spring pressure is significant to load the last 5 rounds in a 15 round mag as trying to hold against increasing harder spring pressure creates pain in my arthritic thumb. I found the RimX and L3i billet (1 lb fucking too heavy) magazine spring pressure to be ideal (for reference).
Having both loading methods is the best options to have as all things change over time.