I made the move from a 2005 H260 to a 2009 Sl262 last year. I feel I can make some good contributions to this discussion. I cannot, however, comment on the passenger seat as the SL262 has a passenger seat that swivels.
As for the sink, I used mine quite a bit on my H260 but to each his own. I did get the sink on my SL262 and although in a tight spot, it is usable and does not infiltrate the cockpit whatsoever. It is especially handy because I mounted my gas grill directly over it
I split time between the ocean and lakes and as others have stated you cannot beat the ride of the SL262. The naysayers of the design probably have not taken a ride in an SL series. Although it looks like a tri hull it certainly is not. In fact, the centerline of the boat is almost exactly the same as the horizon series so they cut the water just fine. I would say that the H260 vs the SL262 (ride quality) is like comparing an upscale american car to a mercedes. It is truly different and everyone that rides in my SL262 that used to ride in my 260 comments that they like it better. To add to the differences, the SL just feels luxurious in every way...from the vinyl to the carpet to the dashboard to the deep thud of the hull in rough water. It is a heavier boat and just better all around in my opinion. Don't get me wrong, the H260 was awesome too, but I definitely feel I upgraded when my Sl262 was delivered (the 425 hp H.O. 8.1L Merc helped

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With one season under my belt with the SL262 I can honestly say I have no complaints. I am pleased in more ways than one...especially now that no one has to move for me to get a cold drink out of the cooler...cooler location is key!
If there are any other questions, feel free to ask. I love the Four Winns brand (I have owned both Four Winns and Regal boats) and think both the Horizon and SL series are great.