I bought myself some Tubus racks a while back for a long trip and while they are great racks, I have successfully used average priced aluminum racks with no issues, both front and back, for decades for the odd tour and tons of miles commuting with panniers on over rough roads.

My take on it is that unless you are carrying a very heavy load and are being rough over bad roads or whatever, a well made alu rack (especially a good beefy one) will work perfectly fine. I have a racktime rear rack that came with a used bike and have put on my wifes bike, and it seems just as sturdy , or more, than the reasonably priced ones I have used for years and years.

again, I see the factor being where you are riding, how much weight is involved, what size tires and pressures (suspension effect) and if you use common sense in not bashing over rough stuff at speeds that will bang the crap out of everything.