@lukass2000 

My decision for this would be based on the clients your currently have, namely the 2x2 or 3x3 clients.  The EAP245 can handle 3x3 connections whereas the EAP610 is a 2x2 so may result in a speed drop if you have 3x3 clients.

The way to check this, see if any of your current clients are connected via WiFi with a speed greater than 866mbps (2x 433mbps)  which is the max speed of an AC 2x2 card.  To be honest, its highly likely your devices are all 2x2, only ever seen a 3x3 when specifically bought for that reason. 

If that is the case, then there are likely to be no issues with performance running your existing devices, and the addition of WiFi6 would be good future-proof. 

In terms of running WPA2 and 3 co-current.   In the controller you can select WPA3 SAE with WPA2 AES in a mixed mode, or just stick to WPA2.

Hardware wise, the EAP610 being a newer AP, there is a definite chance this will be supported longer going forward, where as the AC hardware is likely becoming end of life.