there's no real drawbacks to that style of harness, they are just different, more complex than they really need to be for most people but if you're doing a lot of shore diving where you have a ways to go it may be more comfortable. Try the one piece harness and if you don't like it, you're not out a lot of money and Northeast Scuba Supply usually has the Transplates pretty cheap. I don't dive a one piece harness, I learned on one, have a few hundred dives on them and over a thousand hours in a pool on one, but I prefer the Dive Rite deluxe harness because I need a chest strap. My body shape does not work well with the standard backplate design and one piece harness due to my shoulders and chest being larger than my waist. Beautiful in the water, lose circulation in both arms very quickly on land, no bueno. The deluxe harness is still a far cry from the Transplate though and doesn't have any quick releases. I do have that style harness on my Transpac which I use if I have to hike around with doubles *super rare, but sometimes you have a long trek down to the boat, and it isn't worth switching over to the hard plate once down there, and it is the harness on my Nomad for sidemount, and I will still go back to the one piece harness in the pool since the Halcyon Eclipse is the rig that we have to teach in. I would prefer to be able to use all one piece harnesses all around.
One of the biggest deciding factors is what company you want your money to support.
Scubapro-massive multibillion dollar corporation-Jarden-nothing to my knowledge is made here
Aqualung/Apeks-slight smaller massive corporation-nothing to my knowledge is made here
Hollis-similarly sized to Aqualung massive corporation-AUP-don't believe anything is made here
Dive Rite-pretty small US based company in FL-wings are made in NY, plates are made somewhere in New England, used to be MA but I think it's CT now
Hog-tiny company run out of Georgia, there is talk of them bringing wing production back to the US, but as of right now it is all done overseas
Halcyon-basically run out of a garage- small company in FL-all made in FL
Deep Sea Supply-same as Halcyon but in Pasadena-all made in CA
DSS and Halcyon do have higher quality backplates than the others, JJ and Tobin take great pride in the quality of workmanship in their plates, and while Halcyons work better with doubles because that is their primary target, Tobins plates are superior on single tanks for most people, he also has a bunch of different size plates which may be beneficial to you since you do not fit the normal 6'0" 200lb mold that the current plates were manufactured around, the HP80's are also very short tanks so you may need the shorter plate to have proper tank positioning. You might very well need a regular size plate, but having size options might be worth a few extra bucks. Deep Sea Supply also has a cinch type adapter for their plates, but a properly fitting one piece harness is actually very loose in the shoulder straps so you usually slip down and out from it, very rare you'd actually have to use it. In true emergency you just cut yourself out and replace the $10 in webbing.
Dive Rite standardized the current backplate design back in the 80's, along with the bolt spacing, so they all look basically the same. Same basic size, same basic shape, holes are in the same general spots, the differences are in how well they are finished, Halcyons plates are absolutely gorgeous to look at, and the big one is the angle of the bend in the plate. Halcyons tend to be a bit tighter angle to fit doubles more securely, DSS makes flatter plates that are better for single tank diving as they move the plate closer to your back.
You can certainly go the cheap route and the quality is certainly there, but I am generally ok with spending a few bucks more and supporting the small guys that are really doing the innovation and standing behind their work. Halcyon is very uptight about their reputation in the industry and they stand behind their products as much as everyone except maybe Shearwater in the industry, you'll get tremendous local support from Tobin if you need it, though with those two it is highly unlikely. Dive Rite has always been known for their customer support and it is true to this day, you gamble with the big companies, it's a pretty straight shot with the small guys.