If anny of those lower iv Machamp have 15 ATK iv, they might still be worth the investment to power up.
It also depends how fast you can accumulate candy though. If you find Machop frequently, I would just go for the high iv one since it will perform a little better. (and your others don't have a good moveset yet, so you might get something usefull here aswell, without having to wait for raids to release, since that will prob take awhile)