I've been browsing the web for a build I am planning and I stumbled across Midwest Industries billet upper receiver. I like the aesthetics of it a lot but it's milled from 6061 so that makes me wary of buying it. So my question is, would the aluminum wear away much faster around the charging handle latch catch area compared to a 7075 and should I even bother considering this upper? I mean, It's Midwest Industries so it is probably gtg right?

The MI 6061 T6 billet is perfectly fine....You wont wear it out, don't worry...........well unless you have the ammo inventory of say SG Ammo or Battlefield LV!

It's indisputable that 7075 has better strenght and is bit more corrosion resitance. It's also true that 6061 has been used with no issues by a lot of manufacturers. I think that counts more the better quality control that the manufacturer can assure than the alloy itself. I mean a 6061 upper in spec with high end finish could be better sometimes better than a 7075 upper. I had experience with many MI products and I would trust them even if the upper is Made of 6061 Al. IMHO

There are numerous 6061 billet uppers out there and I have not seen any posts complaining about wear being different from a standard forged upper.
The quality of the anodizing would have a lot to do with wear resistance.

Vietnam era M-16's were 6061, and there are plenty of them still floating around.

I have several Sun Devil 6061 uppers and they are some of my favorites. I use Plastilube on the BCG contact points for all my AR rifles and wear is not noticeably different that any other upper. What they will look like 10,000 rounds down the road I have no idea. I won't be alive to worry about it.