I had a 5.0L GSi/SX on my 1999 Sundowner 225 and a 5.7L GSi/DP on my 1999 Vista 268.
I guess then, I have actual experience with both drives, and the SX with the 225; albeit with a smaller engine. Forget trim tabs, it isn't needed on that boat, at least with the Stable-Vee 2 hull. Later models (2003 and later), I think had the Stable-Vee 3 hull, and I cannot vouch for those.
When we took the 225 for its delivery cruise (I bought it new, then traded it later for the Vista), the dealer had me do tight figure 8 turns at 35mph, and the wife had to hold on real tight in the back seat to keep from going out of the boat. The boat had a lot of lateral bite into the water, and incredibly tracked as true as can be, and there was no appreciable heeling. I was completely amazed.
The boat does have a bit of low speed bow wander, which is typical of I/Os, but so did my Vista with DP. I didn't really notice any more bow wander with the Sundowner. My worst boat bow wander wise was my 18ft Rinker. I think bow wander might be less of a problem as you increase size.
With my Carver, having twin engines and inboards, I have absolutely no bow wander, but I do have wind wander!!!
Any difference was marginal at best between the SX and DP. Of course, if I had the SX on the Vista, it might have behaved a bit different, but the SX, even with the EFI 5.0L was a pretty good performing boat.
One advantage of the SX is that it is easier to change out props, and if you plan on boating in different areas with unknown waters, an aluminum prop on the SX is going to be much less painful if you hit something.
While the DP looks cool, I really don't think it will make much difference on the 225. Buy the 225 that you like the best, regardless of whether it has the SX or DP. Of course, if the boat has a DP and is the same price, well thats great, but don't discount the SX or make it a show stopper if it doesn't have a DP.
For example, I'd take a carburated 5.7L SX engine on a 225 any day over a 5.0L EFI/DP.
Here was my Sundowner:
I actually kind of miss that boat - it was quite nice.