Square/reese/under car type is the best. Better load rating and look. However you will end up with more clutter, plates and brackets to strengthen it. Some bar makers have plates in your boot, others have everything underneath.
The only problem with a "square" type is that some bars can stop you having LPG tanks installed in the future as some mounts can intrude on the tanks space.
(sorry couldnt resist all the info, I now fit towbars for a living

. It sucks)
Steve.