Your question will produce many different answers.
I have a test on an APEX and a ZODIAC Medline and when I dig it out will email a copy to you.
The APEX boats (apparently) are hot in the US due to their very low price. They are built in SAmerica (if I remember correctly-hence low labour costs) and they are supplied with full kit including bimini, trailer and 4-strokes engine.
APEX seems to perform OK in test and comments are good about storage space onboard etc. But when did you find a test in a magazine that does not make the boat that they test the best of the best and even better than the previous boat they tested.
I think you need to go on board a boat you want to buy and test it your self.
Regarding the water spray, On a RIB is a fact that one way or the other you will get wet (even if this means a small splash) so they are all the same or similar on this aspect whatever people say (probably I dug a hole for my self here LOL
ZODIACs are good boats, have great packages (engine/trailer/boat) because people feel apprehensive of their tube material (PVC instead of Hypalon) and from what I am told ZODIAC has not sold many boats in Europe this year.
However, spoken to manufacturers and have got some tests for both tube materials both perform great and they have no differences in durability (both last for 10 years).
Engines, I am a 2-stroke man my self (they have been around for longer time than 4-strokes) and I would say 90 bhp will be OK with a lower pitch prop so you get the acceleration for the skiers (I also water ski and I am 14 stone).
Re Cat B (offshore any weather) and emissions I think that although you can have it in mind, for the purpose you need to use the boat just forget it. It may come into force sometime never.
There are many people who cruise out here with Cat C boats and 2-strokes engines. Just to clarify Cat C means that the boat can cruise in inland waters (what is considered 'inland waters' is a matter of each authority to determine - in Greece is everywhere in the Aegean and Ionian Seas and in the UK covers even the Channel
) with waves of 2 mrs or less. So what do you do when you start with nice weather which deteriorates further on to a force 6 or 7?? No one has answered that one yet!!
Any way good luck with the purchase of a RIB!! Which I may add you will enjoy better in a warmer climate.
PS A friendly advise, NEVER BUY A SECOND HAND RIB
unless you are absolutely desperate