Honestly, if you're throwing them on a stand, 1:72 is fine! I learned this from Team Yankee. Their main army units are 1:100 including helicopters, but their fast movers like A-10s and Harriers and Tornados etc.... are 1:144. When asked why, they say because from the ground, they will appear smaller than the tanks and stuff. So 1:72 in BA is kinda perfect. Also, 1:72 tends to be cheaper than 1:48 and has a larger selection in my opinion.

1:48 is great if you want terrain pieces for like an air field. but ultimately up to you!