Pop: Revise and Extend
After pulling out Louder Than Bombs and comparing "Shoplifters of the World Unite," I'm going to say that The Sound of The Smiths is probably on the nasty side of loud.
The newer record sounds good, but if you have headphones (or a system) with any forward lean at all, you're going to be reaching for the volume knob but quick. The Sound is a little heavier than the Sire Louder Than Bombs, which might be a source issue (analog vs. digital) or it might be because Johnny Marr and the other mastering engineers jacked the bass EQ way up to give the songs a heavier low end. Frankly, I'd rather do my own volume-boosting and EQ (though I try to keep it no louder than 50% with a flat EQ) than have some engineer deciding what I want.
The problem with a prolific band (at least on the singles and compilations front) is that you've got so much floating around that a one-stop-shopping-style collection is needed, but if it sounds wonky, then you might as well make a playlist with Louder Than Bombs and Meat Is Murder. A retrospective box set, mastered well from the original source tapes, would be much needed right now.
Final judgment on The Sound: Pretty good selection (and they pitch-corrected "You Just Haven't Earned It Yet, Baby") and the sound isn't as bad as most records today, but you're still better off with Louder and Meat if you want a quick introduction to The Smiths. Of course, you're best off buying as much of the discography as you get at once, since you might save some money on transport costs.
You'll buy it anyway.