Voltage Sag -- What is the most suitable battery cell?

I tested my Li-ion pack 10s 9000mah on flat ground and got 27 miles Then I tested it on a a road with long hills and only got 10 miles. My 12s 5000/25 would go 12 miles on flat or hills. My 10s 5000/60 went 13 miles with using it up. I’m not just throwing theory out there. Like I said, I learned this the hard way and have proved it myself.