That's a matter of opinion, one I respectfully disagree with. The design of those towers may not be to everyone's taste and perhaps there's nothing really groundbreaking about them either, but they're certainly more interesting than your typical Toronto highrise.
The various design elements employed on the Delta itself maybe rather subtle, but they come together so well that its far more interesting than its basic form would suggest it to be. When I look at Southcore in its entirety, the ICE towers my be the first building I notice, but that has as much to do about their height as their design, as in the end I always find that my eyes trend to settle on the Delta. In fact I find it to be as visually appealing as even aA's best work, the Four Seasons. But as you noted a there is a difference between a business hotel and a residential project like this. Much like if they had gone with aA, we wouldn't be getting the second coming of the 4 Seasons so I realize that P+S won't be reproducing the Detla here either.
All that being said, P+S would certainly be not be my 1st choice either. I'm just ambivalent about them being chosen over aA for this project. That's not to say that aA isn't the better firm in general when comparing the two, they're certainly far superior when it comes to the finer details. But I find it somewhat ironic that you noted P+S buildings as being unremarkable, for I feel the exact same way about the majority of aA's buildings. As well executed as they may be, the last thing City Place needs is a 79s version of U condo/Distillery/Murano/Casa 4/Peter st/Harbour Plaza/etc, which is most likely the type of building they would design here. Basically a taller and somewhat more refined version of everything that's already there. It's been rumored that P+S have designed a 'plus' (+) shaped tower with artwork running up a portion of the building's sides, so I'm encouraged by that news as that's something different, albeit not radically so, than the usual CP building.