You can't make a tow vehicle decision until you know what the boat is.
Find out what what the boat (with motor, trailer, battery, gas, etc) weighs. Then make sure your
tow vehicle has at least 30% excess tow capacity unless you are just towing a mile to the ramp.
Four wheel drive is handy on the ramp.
If you keep the boat in a slip, you need to:
schelp tanks to the boat and back
Pull it and have it bottom painted annually.
Haul your tools to the boat to work on it.
Worry about security.
Buy gas at fuel dock prices (OUCH)
Pay slip fees.
Can you tell that my boat is on a trailer? (17' Boston Whaler Montauk)
Take care, kick butt as required, come back safe.
I agree with what Chuck says, and will add a couple more things to "If you keep the boat in a slip"
* You resolve to doing most all your boating/diving to that specific area
* Increased maintenance on lots of things - motor, fittings, hull, interior or the cover, etc.
*Increased cost of routine maintenance - you have to pay on the water mechanics rates and parts cost versus the shop down the street. Or, if you do your own maintenance, you have to run to the shop down the street, and haul all your tools to accomplish the maintenance, which still might require a haul out.
Also, make sure you know where you will trailer your boat. I live in Colorado, and routinely tow to my houseboat at Lake Powell, UT. That's over the Contential Divide :11:.
I have an older (1997) 3/4 Surban with Vortec 454, 410:1 axles, and every tow option available at the time. And it is marginal on climing at 10,000+ feet towing my boat at Interstate speeds (65+ mph). It also gets poor gas mileage (around 5-6 mph) under these conditions. My dad had a 2003 Ford F-250 Power Stroke (7 liter) turbo diesel does a much better job but still have to watch exhaust temp on the long steep grades at hiher altitudes when the turbo is running at max. And he gets almost twice the MPG over my Subrban. He just boutht a new 2008 SuperDuty F-250 with the new twin turbo diesel, but hasn't towed with it yet, so how much better the 6.3 twin turbo will be in our case it yet to TBD.
My boat is only a 20-ft Ski boat (bought before I started diving) and the whole rig weights less than 5000 pounds. Both tow rigs are rated for 1.5 to 2 times that towing weight! And, they are just adequate as far as power is concerned. I have surge brakes on the boat, and they work fine, but I'm glad that either tow vehicle weights 75% - 80% of what I'm towing. I wouldn't go less unless it's a tractor (18 wheeler).
I guess my point on this rambling is 1) determine what you're going to pull first. 2) Determine where and how far and how often you're going to tow it. 3) Based upon the first 2, don't skimp on the tow vehicle's capability, especially if you're going to be towing anywhere other than on level ground at sea level.