It's larger (obvious), basically has the same ash removal system, but with stainless sweeper blades that tend to hold up better than the regular steel ones on the smaller grill. It does include a thermometer, lid holder, and stainless steel grate, none of which are on the 22.5 inch version.
Whether all this is worth the $149 premium over the 22.5" OTG is a personal call.
In the trading post they are talking about being able to buy a Platunim on line from Target for 199 free shipping. That is not bad for new in box item.
Kevin just so you are aware that is likely the One Touch Platinum not the Performer Platinum.