I've given birth in a semi-reclined position, with my knees up, three times, and twice laying flat on my back with my knees pulled way back. (the flat on back ones were 1. because DD's heart rate was dropping and they wanted oxygen on me, and my knees way back to push her out ASAP, and 2. because DS wouldn't come out any other way after trying multiple positions.)
Semi-reclined has been pretty comfortable for me - I've had no desire to try something else. You'll know in the moment, and the difference will be whether you have a care-giver who will encourage you to take any position you like, or one who will want you in a position that suits them best.