As far as HPDI's, they are one of the most reliable engines Yamaha has ever built in the 150-200hp range, larger hp had issues due to a different block design. Range will be better then 4 strokes, and cruise speed will be faster, overall operation cost of 4 stroke vs hpdi will be the same when you add in oil burned from a 2 stroke, but less fill ups needed for the hpdi, and you can get places faster on less fuel. Yamaha has fuel burn numbers on their website for both engines to compare if you wish. As far as spinning the boat, you will need to power in reverse harder the forward and practice, but it does spin with a slight crab to it, it will not spin on a dime like an inboard, but no outboard will, it is more like a spin with maybe 1 ft of movement for every 15-20 degrees of turning would be my estimate, but the boat is nimble, plus the center helm gives you great view for manuveuring, and also gives the boat a smaller feel when operating it. The aft motor well is dry, I tuna fish and back down at times on marlin and tuna, can do 6mph with no water in cockpit, at 8mph you get a small trickle from the corners where there is no piano hinge, but it finds the scuppers located right below them so no water build up ever. We backed down on a fish this year and had to watch stuffing my engines under waves more so then water on deck at the rate I was going. Gate never falls down as long as you have the 2 clips tightened right, it will hold anything you throw at it. The ride is good, a step up over the gulfstream from sheer size and weight, but handling is similar over all, you will handle seas slightly better but not an amazing difference. What you will gain is much more cabin space, and easier passage at the transom when fishing, also more seating at the helm for the crew to get out of the elements. Headroom, there is just 6' of head room, I'm 5'11 and can stand up straight, if my hairs long it might touch the liner above, when short or normal I do not, so if your over 6' you will slouch slightly, but honestly how often are you in there standing? The v berth is avg size, if your taller you can put your feet on the sink portion and it basicalyl extends the length for once person also. From a layout standpoint it is a lot more boat, ride wise you will see an improvement but only in relation to size, a 2 ft jump is not a huge one, typically 4ft is the industry standard for those jumping up, but in smaller boats every 2 ft you do get a bit more boat. No matter how big you go in an outboard powered boat under 30ft, its still an outboard powered boat so sheer hull weight is the only advantage and change, they all ride similar, some boats better then others due to hull design, but all similar in the end. The 265 hull is very dry, much drier I find then most other Grady models, it is rare that I see spray on my windows, it usually takes a cross wind at over 15mph to get spray on the boat, or really nasty seas. As far as capability, they can handle more then we can, I've run mine 110nm in 5 ft seas to the canyon to tuna fish with out thinking about going back, just need to find the right trim angle and speed and your set. The 265 typically likes tabs up and engines up, but in a small chop she likes tab down a little I've found. Just need to play around and get a feel for its sweet spot. Also the boat runs better using the main and leaving the aux empty, otherwise burn the aux off first always. As with any purchase, sea trial it to be sure its what you expect. If you have any detailed questions or further questions feel free to pm me and I'll get back to you as quickly as I can. Best of luck in your decision to move up!!