Welcome to the forum.
Without risking a riot on your first question by comparing boat and engine combinations, then you need to visit some RIB manufacturers. Buying new, then you're in the enviable position of not having to worry about condition of the tubes and hull on a used boat, and the hours or indeed level of maintenance on the engine. Be warned, a 6m RIB and engine combination, fully kitted out, and road trailer won't be cheap. Buying new means you can specify the layout to a degree, seating configurations, engine horsepower (up to the hull rating), tube colours, including reinforced wear patches, tube handles, deck finish, etc.
All the boat makes mentioned will do what you want. You might also want to consider Ribquest too. There are plenty others. You should be looking for a deep V hull with jockey style seating with supporting backrests. Regards seating, then depending how deep your wallet is, then you can go for shock mitigating seats such as Scots Seats.
On the engine side, all the big manufacturers produce 4-stroke marine engines more akin to a modern car with onboard engine management and fuel injection systems that make them powerful, quiet, and relatively frugal, and will come with a comprehensive warranty You'll probably be looking at the 115hp to 150hp range.
If you're looking at having it afloat in a marina, then consider anti-fouling the hull from new, or some other way to stop marine growth such as investing in a Versadock.
Sula
BLACK PIG
Piglet
spy-sea-one
