The position of one's feet on the ground while sitting on the saddle has absolutely nothing to do with proper saddle height. Many 'foot-forward' design bikes, like a lot of dutch models, allow one to put both feet flat on the ground while seated on the saddle.

The (most) proper way to find proper seat height is to look at your legs while pedaling. You should be almost able to straighten your leg completely at the maximum pedal distance. If you can completely straighten out your knee, it's too high. If your knees are still very bent, even at maximum extension, then it's too low.

If you're having soreness issues, it's likely due to both of those saddles being padded. Padded saddles tend to cause more soreness because they transfer pressure from your sit-bones (where it should be) to your soft tissues (where it shouldn't). Also, just keep riding. The only real way to fix soreness is to 'toughen up' the parts that are getting sore. Make sure you're riding 2 or 3 days a week minimum and at least an hour or two at a time.