Oi ! Let's try and stay on topic. And mr.powell, The hellcat will be different, otherwise relic would not add it in :P We already know it will have an MG added to it. So let's keep it at that before we go even further into our off road debate
The point of the new units are that they should present an alternative to the unit they exchange, and the hellcat might just present a faster yet weaker wolverine type with an mg also making it effective against infantry.
The staghound on the other hand would for the british give them something faster and more agile than the stuart with some added abilities most likely.
The american will apparently get the possibility to exchange their greyhound with a stuart, giving them a bit of an earlier armoured punch.. though i am not sure what abilities it could have to make it different from the british one.
Yet i am not sure what it is what will make the schwimmwagen different from what it is it will replace.. and i am curious as to what it is actually the axis will receive beyond that and the hotchkiss.