If everything you have is working fine, there’s no reason to change them.
The primary benefits to Z wave plus are longer range, somewhat easier pairing in place, and better battery life. I doubt if you’d notice much energy savings just for a mains powered switch of the new generation, certainly not enough to justify the cost.
I’d stick with the switches you have and then when you need a replacement, use the zwave plus model.
If you’ve got extra money in your home automation budget, the following might be of interest.
If you don’t have extra money in your home automation budget and you’re considering swapping out all your existing switches for a newer model, then you might check the following thread instead:
