My experience says there is a difference. Allow me to offer one possible reason. A good framework gives a project a good structure to start with. Most homegrown solutions have to recreate much of the structure of the framework, and they often do a worse job than the highly developed frameworks that have the experience of many open source developers behind them.
All other things being equal, a "homegrown" project by coders who know what they're doing is going to be better than a framework project by coders who don't. Yes, I understand your reason, and given coders of equal ability it may be true; but I've seen Django projects written so badly the framework made very little difference to maintenance overhead (and as Django becomes more popular and mainstream we're going to see more examples of this).
Even a team of good coders often produces a worse homegrown solution due to the time pressures of their project. This in my opinion makes the chances of creating a better homegrown solution low. And you lose all the reuse abilities you get from a framework.
