hardstyle aikido imho means less on the gentle side, uke may feel some pain (calibrated) depending on the techniques being practiced, and lots of hard falls (ukemi).
again, its just my opinion. i concede that meaning of "hard style" aikido can be relative
I hear that......
We have quite a martial style in our dojo. It tends towards classical on fridays but wednesdays are pretty technical. It's a nice mix of both but even our more classical night is pretty martial with regards to how we practice and apply techniques, it can be sore but gives you a good idea of why you need restraint in aikido.