I did a century on a rigid mtb once. Ezpz century, riding and chatting with a buddy the whole way. It was over before we knew it. The only Dutchifucation was running 1 1/4" slicks. No pain, just a day of easy miles.

Another time I did a two-nighter riding an old Schwinn 3 speed with swept bars. Day 2 was 90 miles. Panniers, tent, sleeping bag, food. Roads were mostly chip seal. Again, not an ordeal, just a few days on a bike.

At Paris Brest Paris, a 1200km 90 hour ride, you'll see every kind of bike known to humanity, and a few home constructs nobody has ever seen. Any kind of handlebar made will be there. You'll see a dude on a pure race bike sporting an ill advised 20 lb backpack, and another dude on a flat bar fixie carrying nothing but a light rain jacket.

For a nine mile commute, ride whatever makes you want to get up in the morning.