Gentlemen,
Thank you all for your feedback and insight. It is a very close call as both manufacturers are highly recommended. Fortunately, my 2003 F225 did not have the exhaust issues of almost 20 years ago, which I worried about, and I noted the lackluster customer service response by Yamaha to address that issue. My sense is Yamaha did not take that problem lightly. In searching for a used F225 or F250, there are very few if any manufactured after 2006 for sale, which I think speaks well for the quality of newer models.
The Honda's longer warranty period and slightly lower price are tempting. It requires new rigging, though. It is good to know my marina is an authorized dealer and has technicians for both brands and that Honda is a very equivalent and formidable alternative.
I also called Grady White's customer service rep since Yamaha has been GW's partner for over 25 years. For whatever it is worth, I will stick with the F250XB. After all, a Grady just wouldn't "look right" without Yamaha power, right? Many thanks!