The Tomorrowland parade crossing waiting area gets pretty full pretty fast, so I don't know that there is a huge advantage to trying to get to MS via TL. I was there in mid-October, the parade crossing periods weren't long enough to clear out the crowds waiting to cross, so the back-up extended past Astro Orbitor. As mentioned the parade route filled up pretty quickly and by the time folks in the TL area got into the Hub area, most of the "best" spots had already been taken (the prime spots will be filled up with guests waiting from well before PtN starts). Personally, I would try to watch PtN from wherever you want to watch fireworks. So if you want to watch PtN by IaSW, I would find a spot along IaSW Mall to watch fireworks and not try to get down to the hub/Main Street.