If you are looking into getting the current SEVERE, it is made of delrin plastic. The Genesis on the other hand is made of metal. Likewise, the Genesis will naturally outspin the SEVERE just to get that out of the way first.
But now I’ll talk about play.
In comparison, I can saw that the Severe plays lighter and faster than the genesis. This is due to its shape. The genesis has all of its weight in the rims which makes it play slower. However, the Genesis is way more stable. At high speeds, the Severe will move faster, but lose control quicker/easier than the genesis.
In my time I have owned 3 genesis, the OG genesis, the 7075 Doomsday, and the hubstack Genesis. I have never played the newest one, but my history with Genesis is that it is a solid player and you cannot go wrong with it.
If you are interested in learning 5a, I will reccomend the Severe over the genesis. The severe, being plastic, will be able to survive dropping it and dinging it with the counterweight more than a metal yoyo would. I also find learning 5a tricks to e easier on a plastic yoyo versus a metal one.
If you are looking for an all around yoyo that you can do 1a and 5a with, I would say go with the Genesis. Mostly because for the same price you can get a metal yoyo versus a platstic yoyo.
However, if you happen to find a supernova for cheap, the metal sister yoyo to the severe, I would get that over the genesis. The Supernova is a hell of a player.