It's a good idea to wait until you see a flower or two before taking them out of veg but it'll flower eventually under the 12/12. You should start to see some white hairs on the tip in a week or so. At worst, it'll be a little behind the other one. Probably best to take cuttings from the quickest flowering one though, if you want fast ripening. It looks like a more Indica dominant pheno, which is probably why it's flowering faster. Indicas are generally faster than Sativas. But the other one could turn out to produce larger buds or better smell/flavor so I would take cuttings from both and label them, then see which mother plant turns out best and keep that clone for propagating. Also, if you grew from non-feminized seeds the smaller plant could turn out to be male, which are often thinner than females.