5&3/4 should be close enough for most things, it depends on the trailer too not all of them have the coupler set to the exact same height, the main thing to watch out for is you don't want the trailer tongue/bed leaning backwards, there has to be tongue weight and at least level or even slightly forward cant in order for it to follow the vehicle properly and be safe.
For a hitch ball I have one of these swap-a-ball systems and its pretty decent for the convenience factor, you literally just push the pin out and swap whichever size ball you need at the time. They have another kit with a third size ball but I've never needed it (nothing that uses a 2-5/16" ball is going to be light enough to tow behind the Compass...)
The pros of this are
1) You get the two major sizes available to you at all times while carrying the least possible amount of extra weight / least amount of "extra things" to stow with the spare tire.
2) Its (usually) fairly fast and easy to change.
3) Easy to change ball size even if you are using an anti-rattle plate bolted to your receiver like I do.
The cons are
1) If you leave it installed and drive around a whole winter without touching it, the ball might rust to the shaft like mine did, then it is not as quick/easy to change, had to hammer it off and then polish the rust off with a wire wheel. I now put some grease on it to reduce rust buildup.
2) Since the ball is retained by a cross-pin it can move a hundredth of an inch or so. Just enough to allow for some minor metallic rattling potential with an empty trailer that isn't pushing down on the ball hard. Thick grease helps reduce this too somewhat.
Overall I like it. I am able to stow the entire drop hitch with the swap-a-ball stub permanently bolted into it on the driver's side forward part of the spare tire compartment, with one ball on the stub and one ball wrapped in a rag so it doesn't do any metal-on-metal rattling. In about 60 seconds I can install the drop hitch with whichever ball I need and I'm ready to tow.
As a side note, most small and medium uhaul trailers have those couplers that work on either 1&7/8" OR 2" balls, you spin the square nut thing and it adjusts to fit, so those trailers are a non-issue. If every other trailer you could potentially use will be 1&7/8", you can run a cheaper solid ball which saves a couple bucks and can potentially be a tiny bit quieter with no moving parts. For me, most trailers I use end up being 1&7/8" but there are just one or two bigger ones I occasionally borrow that are 2" so with the swap-a-ball all I have to do is keep that extra 2" ball wrapped in that rag by the spare tire and I'm ready for whatever.