Hello there. As far as comparing it to the Shamrock, I have no idea. My MS Pilot had the 240hp Yanmar. It was fairly noisy but not overly so. A friend of mine has the 230hp Yanmar in a 1998 Pilot. His is a lot noisier than mine was. But that is likely just a function of sound insulation. A lot of the noise comes from the harmonic vibration thru the hull...which should be much less with the 6 cylinder.
As far as wet ride goes...you can't have your cake and eat it too(in a small boat). You either have a boat that goes THROUGH the weather/waves. Or you have a boat that goes OVER the weather/waves. The one that goes THROUGH the waves is a better sea boat...but as you might imagine, going through it will cause spray and a wet ride. That is the case with the MS Pilot. Great ride...but a wet one. If you were going OVER the waves you would obviously end up with a rough pounding ride.
Another thing to think about in your vintage range of searching.... Mainship did a remodel on the boat in 2003 hence the Pilot II moniker. While it doesn't look like much, it was fairly extensive in my opinion. The first thing is engine options. I do not think you have an option for the 315 Yanmar on the earlier version(2002 and older). Secondly, the hull shape is totally different. The earlier versions are a classic semi displacement hull with a keep and the propshaft exiting the back of the keel at the rear of the boat. The II version has the keel cut away and the shaft exiting about midship with a carrier/shoe that takes the exposed shaft all the way aft in a prop pocket. You will notice earlier Pilots have a draft of 2.10. The II version has a draft of 2.2 because of the pocket. Not only does it reduce draft but puts the thrustline more parallel to the longitudinal axis of the boat making the thrust translate to forward movement as opposed to a (bow)downward moment. The shape of the hull is also fairly different. The cutaway keel allows for a more planing like hull taking advantage of the efficiencies of a planing hull versus a semi hull. AMazingly, you would expect the newer hull to pound more since it is flatter throughout the back half of the boat But it does not. It rides very well and is faster and more efficient.
Lastly, the interior of the II version is very different. Marketing wanted a centerline queen and by golly, they got it. At the expense of the forward half of the interior space. I personally don't like the newer interior. I like the V berth set up as it gives you interior space all the way to the forepeak. With the II version, you hit the landing of the companionway stairs and that is pretty much it. You have a few more steps forward and that it all you got!!!...the folded up queen bed taking up the forward 7-10 feet of the interior of the boat. 7-10 feet of VERY PRECIOUS space!!!
My final opinion of the boat after 6 years of ownership....an EXCELLENT value in an EXCELLENT DAY boat....DAY boat. For a 30 foot planing powerboat, you are not going to get a more efficient boat. The only reason I do not still own it is because it is a little small. OK, it is VERY small. You are still somewhat camping sailboat style. There just isn't a lot of space for all of the creature comforts you get in a larger boat. If you can stretch for the MS34 Pilot, I would try. It gives you much more space. Anyway, I loved my MS Pilot. Fantastic boat for what it was(a day boat). I just wanted more comfort. The lack of comfort forced me into a certain type of boating....day boating. If you are more inclined to camping style boating, then nothing wrong with that and I know a definite step up from the Shamrock.
Prairie 29...Perkins 4236...Sold
Mainship Pilot 30...Yanmar 4LHA-STP...Sold
Carver 356...T-Cummins 330B...Sold
Meridian 411...T-Cummins 450C