I have an older straight load - it requires some convincing to get my horses into it. My second trailer is a slant load - it requires no effort to get them into it. So, needless to say, I have a strong preference for my slant load.
Size is important with the slant load. Mine is 7 ft high and about 6.5 ft wide with about a 7.5 ft stall length. The tallest and longest of my horses is 15 hh and its pretty much a perfect fit for him and he seems very comfortable in it. I don`t think I would like to put your 16 hh in my slant more because of the length issue than the height (although all is relevant). Bigger slants are available on the market, as well as straight load 'warmblood' models for the more substantial horse.
My slant does not have a saddle compartment in the back. To load I open up both big and small doors and it gives a nice spacious appearance to it, something I could not get with the straight load. The other thing that I do with the slant is to lead my horses out (not back them out - which I am sure is another debate in itself) and they are very content with that. I had to put a ramp on the straight load to solve a couple of problems I had with two horses - one of who didn`t like that step up and the other who didn`t like taking that first step back. Problems that have not presented themselves with the slant I believe because of my aforementioned comments on it. So if I did buy a straight load today, I would buy one with a built in ramp.
Before I got my new slant a couple of years ago, I made a list of all the must have and nice to have features I wanted in my next trailer (I was on a budget so was prepared to give up somethings but not all). I checked out web sites and magazine articles I could find on the subject. I skulked around horse shows and dealerships checking out units. I talked to the occasional trailer owner when they happened to be innocently standing by their trailer. I would have bought used but couldn't find one (essentially in pristine condition) to suit me at the time so I went new. I didn't end up with a luxury model but I am quite happy with the one I did get. My must haves included things like rubber bumper, rubber mats, torsion suspension, electric brakes on both axles, walk in tack room, screened windows that opened on both sides, roof vents, interior lights plus size of course.
By the way, as an informational item, my sister hauls her two horses loose in a stock type trailer. One chooses to face front, the other to face back -- both standing at slight angles.
Good luck in your quest.