I agree completely when lesser assets are Mitch Nay and Dwight Smith Jr. or something outright ridiculous. But Stroman is an elite asset by himself. Consider the fact that Sonny Gray ranked 31st on Dave Cameron's list of most valuable trade assets this season. At the time (July 15) these were Gray's career stats:
2.75 ERA
3.07 FIP
3.27 xFIP
189.2 innings (29 GS)
Stroman's stats since being moved to the rotation:
3.27 ERA
2.82 FIP
3.18 xFIP
118.1 innings (19 GS, 1 RP)
Those are fairly comparable stats and Stroman has an edge in age (1 year younger than Gray was at the time), so I think it's fair to say Stroman is arguably at the back end of the 30 most valuable trade assets in the game. Of course Donaldson ranked 17th, and would probably rank a couple spots higher now, so Stroman vs. Donaldson is a pretty easy call. But Pompey is arguably a top 50 prospect, no doubt top 100 prospect, who is close, and Lawrie is going to be a relatively cheap regular for the next three years with upside remaining. I actually didn't realize Donaldson was a Super-Two and had 4 years left, so that makes it a lot closer. But I still lean towards the Jays package. Like I said, it's probably a lateral move (or marginal upgrade at best) for 2015, and if the team is giving up future wins (which I'm not opposed to), it needs to be for a bigger 2015 swing. One other thing to consider as well; the Jays still have a chance to lock up Stroman to a team friendly deal and could do the same with Pompey eventually.
I think it's a moot point in practical terms though. Since Donaldson has 4 years of arb, I think it's much more likely they look to move him next offseason or the offseason after that. They can afford him for at least 2015 and he'd still be incredibly valuable with 3 or 2 years of arb control left.