Welcome to the forum.
Wish someone left me a choice of two Seariders!
Without doubt go for the 5.4m in my opinion. Plenty of advice on the forum about Seariders, and very loyal following. If its cosmetic work such as cleaning tubes or servicing the engine, then everything is possible. Double check the transom and deck, as they are known areas to go if not properly maintained, etc.
The 4m Searider is still a great boat but the 5.4m gives you options for extra fuel and kit, and plenty space on board if taking friends out as your knowledge and experience increases.
Regards the 60hp, yes you don't need to use it in anger but with 4 people on board, full kit and fuel, then you'll need all your horses.