In 20mm puttin g the toys on the table is a lot cheaper. I never found scratchbuilding harder though, I have a large collection of vehicles modded after various pictures from various warzones, and a bigger vehicle doesn't make it easier (My 40K Orks cost me a fortune in plastic in bits compared to modding 5 euro plastic Revell Humvees into ISIS ones, for instance)
Just a thought, how often are you going to use that chopper in a game? Would a few trucks or landrovers not be much more useful? Open top the Landi, put on a FN-MAG or a Bren on a pintle in the back and she will be on the table almost every time.