This trade isn't a slamdunk, although Mike and kevin are correct that Rivers is a better pitcher (maybe about 0.4 of ERA better, plus he'll pitch more innings). You have a ridiculously good rotation-- either of these guys really is your SP5. Thus, you're giving up 11 seasons of control of a solid young SP3-4-type to upgrade from one guy who isn't going to start for you in the playoffs to another, which I don't get.
If one of your other SP is going to be an FA at the end of this season and won't re-sign with you, then take this trade. Otherwise I'd look to trade Reynolds for a major position player upgrade.