You have several possible conflicting priorities to sift through. If ride quality & interior room fits into the 'mix' somewhere, then the Accord is the preferred way to go. Both models have lots of mods available, however the Si has more related to performance. A stock '07 V6 MT Accord will slightly outrun a stock '07 Si. However, you'll find forced induction kits for the Si that you won't find for the Accord. You'll also find more chassis, brake, suspension, and body kit upgrades for the Si as well...it's really more of a "tuner's" car. But if you look beyond raw acceleration numbers, the Accord is a more refined vehicle.