Model year doesn't matter at all. But some options/features weren't available on earlier cars (folding mirrors, parking sensors, etc) and only came out in late 2013. So you have to compare the options, and the model year itself isn't as meaningful.
People LOVE their P85+. I've never driven one. If the options were similar, I'd probably go for the + in a heartbeat, especially if it were less expensive than a new P85 without the +.