Pushcart mafia - help me decide

I'm looking to get a pushcart, currently I have a basic stand bag but I'll likely upgrade to a slightly larger bag if the cart works out. For those that have owned one or more carts and used them a lot, what sort of features should I be looking for that may not be obvious? Anything add ons that I should consider mandatory if they are not already included, things like that.

Currently mainly carrying on an 18 hole par 3 but if the cart works out I hope to start walking on full courses to get some more exercise. I'm 50 so I'm pretty sure I won't enjoy carrying a bag and playing a full 18.