Installing lowers loading speeds. This whole "when it's reading off the disk and HDD at the same time it speeds it up!" thing isn't how it works. If it was, installing would never speed up load times of 360 games. Instead of that happening, it universally always speeds them up. All not installing a disk gets you is a broken 360. Mine is a 2004 model and has only needed repairs once... For a graphic card failure. You don't install games-you deal with longer load times and a far high risk of a dead console. Spreading information that you're better off not installing won't help anyone.
And if that is somehow true, I'll get the PS3 version. I'm not going to put my 360 through the hell of actually having to stream off the disk, I'm not tolerating that for one game that decided to break the rules about installing.
Like i said look up digital foudnry if you need video evidence 
Its got to do with available bandwith troughput over your BUS pipes
See it as a sewer, put to much in it it gets congested.
It constantly streams of the HDD (the install disc) using BUS1, when you use the DVD it streams the play disc to your computing units trough BUS2. Now this was circumvented with GTA V by installing the play disc to a USB device, so it would still follow a different route to your GPCPU, not exceeding the bandwith the HDD could transfer to the CPGPU.
Now this issue is at the moment only happening on the 360 mainly with open world games due to the amount of data being streamed. No flaw in the console, since 9 years ago they couldnt have foreseen this.
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Your arguments are complete failures, ofcourse theyre not going to spend time on old consoles.. they're end of life.... theyre doing you a service releasing at all on that hardware!
Why do you get blocky textures? because ALL the hardware is occupied trying to run the rest of the game in an acceptable standard, which barely just barely is working..
FPS already takes huge drops in combat.