If you live close to Humber you can easily get a boat serviced if there's any problems. My experience of the company was very positive. The logic of each design feature and the reasons the boat was built the way it is were explained in detail and it was obvious that I was talking to seafarers who built boats, rather than 'businessmen'.
I don't think you can compare the Assault and Ribcraft directly - shallow and deep V. Have you thought about the Humber Destroyer? Picture of mine attached. She's 7 years old now, kept afloat all season, and I've had no problems.
My son bought it (with a little help) when he was 15, did his level 2 and away he went. You can guess how he drove it.
The Dorus Mhor is 4 miles away, the Gulf of Corryvreckan less than 10 miles. You can guess where he used to play and what he got up to. (Lest the holier than thou's feel like getting involved, Oliver had spent most of his life at sea under sail and in small outboard powered dinghies.)
Suffice it to say, the boat was driven to it's maximum capabilities and came through with flying colours. She's the only RIB I've owned, but I've seen lots and to my mind, few compare favourably. The large diameter tubes and raised bow of the Destroyer give a great sense of security and seaworthiness in rough water and the deep V cuts through the waves beautifully.