I didn't say you do 5x5. Surprising as it is, this thread isn't about you. Surely you are aware that 5x5 is a pretty often used weight training scheme.
Again I ask, what do you think is the difference between 5x5 and 8x3?
Interesting question, so I have to take a look at the numbers. Say I squat 400, and I'm going to do a workout at an intensity matching my current max, in order to make strength gains for an improved future max.
A conservative estimate of weight for a 5RM would be about 87%, or 348. A conservative estimate of weight for a 3RM would be about 93%, or 372.
So the comparison would be 5 sets of 5 reps with 348 vs. 8 sets of 3 reps with 372.
In the 5x5, total weight lifted is 8,700. In the 8x3, total weight lifted is 8,928. Plus, you're working at a higher percentage of your 1RM. So I'd guess your legs would get more of a beating with the 8x3, seeing that it's more volume and a higher weight lifted.
(Volume overall isn't a great measure by itself. 10 sets of 10 with 135 is 13,500 pounds total lifted, but you're not going to be blown out by that workout as much as 8 x 3 x 372.)