I have over 26K miles on my straight-bar hybrid. Until Covid-19, I used it primarily to do a 34-mile round trip commute twice a week, and it has served me very well. For me, the issue that I have with drop bars is that I cannot comfortably angle my head up very long to maintain good situational awareness. If I just move my eyes to look up, then I end up looking over my glasses and I cannot see anything.
I have not yet attempted a 100-mile ride, but I have done several 75-mile rides. Like you, I plan to do a century this winter when the temperature cools down a little here. On longer rides, seat time has been my biggest issue. My bike has end bars, and I have never felt like there was a lack of hand positions.
As was suggested in another reply, go with the bike that feels the best on your longer rides. Be safe and good luck on your upcoming ride!