I had an 09 2.5i with a 5MT before I got my XT. I've also driven a 5th gen with the CVT and with the 6MT.
N/A Subarus haven't gotten any faster since the early 90's. If you find that kind of performance suitable, then you will be pleased. If you don't, then you will feel that the 2.5i is underpowered. Personally, I was extremely depressed at the performance of my 2.5i. My car did have engine problems, but they were related to drivability and not power. It was pitifully slow, obnoxiously loud, and very boring in general.
Forget passing or rapid merging. You will come to rely on the kindness of strangers while merging on the highway.
I'd consider the 3.6R as "acceptable", with the 2.5GT being the "sporty alternative". I'd consider the 2.5i as a safe, slow car that parents might consider buying for their teenage rookie driver.