I had the old style Magicalls with the aplix (looks like velcro but much stronger/more resilient). I had no problems with the fastening at all - I prefer that to the snaps as you have more flexibility in the sizing. DS2 self-TTd before taking his nappy off really became a problem, sadly that's not true for DS1, but he could undo snaps as well as anything else (even with the nappy on backwards LOL) so I don't really think that makes a difference.

As for absorbency, they worked really well for DS2 - with a booster we used them almost exclusively during the day. But DS1 was too heavy a wetter for them. He used them at day care but I rarely used them for him at home.