Long and technical. Read at risk of brain explosion
I am a fan of stuff on the roof over the rear hitch especially Skis.
Here in the PNW where mountain passes can have all kinds of road conditions in the same trip, road spray mixed with cinder dust...(think red mud), slush, and Ice, the back of the rig picks up a lot of dirt and grunge, as does anything attached to it. Skis do little to change the CG of the vehicle.
I have gone to roof mounted bike racks over rear, primarily because of access to the hatch (yes I know that some racks swing away) and because with a good roof mounting system, the bike is secured in a way that it will not bounce or twist. (How many bikes do you see attached to the rear of chase cars when bike races are televised?) I have used roof bike racks for 20 years and the advancements in the mounting systems, along with lighter bikes makes this task easier. On the down size they can be difficult to lift up, and do raise your CG.
Bikes on the back of the rig are easy to lift on and off, but can bang each other, bounce more, and in some instances (poor rack design) contact paint. I have also seen tires baked from long trip exposure to the exhaust. That said, a high quality hitch mounted bike rack can eliminate most of these issue.
Lastly, you are hanging a lot of weight on your hitch. If you decide to go hitch, definitely go with a class III. A class one hitch frame is rated for a vertical load of about 200 pounds at the trailer ball. A III is usually 500 or more pounds. The manufacturer engineers the hitch to handle the downward force of the tongue weight at typical ball location. This is generally 3 or 4 inches out from the vehicle. A bike rack, by design moves this load away from the vehicle, as much as as 16 or so inches from the rear of the vehicle. The additional shaft length of the "stinger" on the bike hitch acts like a lever, multiplying the downward force in proportion to the length increase.
So if your bike mount weights 40 pounds, each bike 20 or so pounds, and you hang 3 bikes on the mount, you are at a measured weight of 100# and that would be your measured tongue weight. Except the weight is much further out, which significantly increases the downward force on the fixed mount. So you might have a calculated tongue weight of close to 200#s or more! And...when you go over uneven surfaces, the bikes will bounce a bit....(think of how a lever multiplies force) which can raise this number much higher for short times.
I realize this is a bit extreme, but I have seen hitch failures due to high tongue weight.
Gary