The best backup system is the one you'll actually use.
No backup system is worth a damn unless you've tested the backup copies to make sure they actually work.
A backed-up copy that's stored in the same building as the live files is better than no backup whatsoever, but not by much. One that's on the same computer is just barely better than none at all.
Don't think just a single backup, think multiples: 1 for each of the 7 previous days, 3 more for each of the previous weeks, and 11 more for each of the previous months.
No matter how spiffy your hardware or how extensive and amazing your software, and no matter how much they cost, they'll always be easier and cheaper to replace than your data.
