Here's a take.
Do you know about the different muscle types ?
(Type I, Type IIa and Type IIb)
Working with RM (1-5 rep sets) builds Type IIb muscle fibers, which is the largest, most explosive strength, anaerobic muscles.
Which means, if you build just this type, you'll get tired very fast.
You'll get faster muscles, stronger, bigger, but endurance will be shit..
So it could be an advantage to work up the rep amount as time passes, building more aerobic muscle fibers as well
the 5x5 looks good for building, but remember to work some endurance as well, so you don't end up being tired from walking up stairs and shit.
Mass is good, but make sure your body can take that mass.
Just my 2 cents.