tamron lens’s probably your best bet for ruggedness and reliability, in my expirence they are of a better build quality than canon’s own… i’ve got a tamron 80-300mm on the front of me 350D. i’ve also a 85-210mm made in the late 70’s for my Konica T3 and its still as good as the day it was made.
I’ve owned a couple sigma lens’s over the years but not impressed with the build quality, they’ve either ended up in the bin or being given away for spares!