from my personal experience, it affects the flying time a little bit about 1 min (not so sure).
but to me, I use
Tello in a light wind condition for taking short drone videos or maybe just playing around. If you're flying it in high-windy place, you'll never gonna think about taking of the propeller since it could be blown if it's too light-weighted.
Prop-guard is a bit better attached, you know keeping the weight down a bit.