For someone who is 71" in height, would you choose a medium sized bike (17.5") or a large size (19") according to the specs:

MD (17.5") -- height range 68.3–72.9"

LG (19") -- height range 71.3–75.8"


In general, is it better to go for a smaller size frame and if necessary just increase the stem length? Are there any advantages of choosing one size over the other in terms of ride performance?

get on the bikes and test ride them. that is the best way to test if they are comfortable. there are some general guidelines around how a bike fits, but i believe a lot of it is personal preference.

I think the general rule of thumb if you are on right on the line and one doesn't really feel better than the other is to go with the smaller size.

go smaller, you can always get a longer stem and seatpost

+1 it's lighter too!

71" eh..so that is...5'11"...I would go MD 17.5". The reason is my friend who is 6'3" found a 19.5" LG too big....he switched to a 17.5" M after and its perfect now...consider that you are not even 6', you shouldn't go with large. Your shop might says large...but test it yourself, see if you can pull ur front wheel off the floor on a flat surface standing at least 2" and the best 5". It also depends on what bike you are getting...if a FS, MED for sure...don't even try large.....top tube length can be fixed with stem, bars and pedal position can be change with seatpost, and crankarm length....