I have never used a loader, but I have the WiiKey V1 and I can say that so far I have not had any problems playing backup games. The most trouble I have had was with Monster Hunter Tri and it was trouble on the Wii firmware's end needing to be updated. If you do get the WiiKey V1 be prepared to do some pretty basic soldering and make SURE you get the 1.9 Update from the wiikey site BEFORE you let the console update (though the chip may come updated now, idk, i did mine a long time ago). I can't say for sure it will have any bad effects if you don't but there are tales of bricking if console updates before chip.
Install - 4/5
Reliability - 5/5
Ease of Use - 4/5 (updating is simple but discs need to be burnt and it isn't the most user friendly system man has ever devised)
Risk - 4/5 (While there is always physical risk involved in soldering chips, the risk on the software side of this one is very minimal since it DOES have a stealth feature and seems to be updated past the era of bricking.
Good luck.