I agree
Here is the thing: if it comes down to those two boats, I have no doubt that the MR Explorer 15 would be “better” to paddle solo. But in my opinion, it is not a desirable solo canoe. With a gunwale width of nearly 36" amidships, it is just too wide to be able to utilize cross strokes effectively, and even a decent onside forward stroke may be challenging if you are sitting centered near amidships. The 15’ Explorer is wider amidships at the gunwales than the 16’, by the way.
You currently have a tandem team weight of 375lbs without clothes or gear. In all likelihood, that will be way over 400lbs in a year or so, if you and your son are still paddling together. I think you will find the MR Explorer uncomfortably small loaded for overnight trips with two paddlers. It is a safety issue as much as anything. And there will be a very limited space behind the center thwart for packs.
In my opinion, if you bought the 16’ Explorer you would have a quite good tandem tripping canoe. With the 15’ MRC Explorer, you would have a boat that compromises both solo and tandem usage.