They're sort of similar. There's no trade element to it, and there's a ceiling to how many ships you can have and how big each of those ships is allowed to be, so you can't work your way up to a fleet of 20 dreadnoughts. Combat's also fairly different - combat in SPAZ relies pretty heavily on the mouse, where I recall being able to ignore the mouse completely for EV.
There's an open-source game (currently on Steam, even) called Endless Sky which is intended to be a spiritual successor to EV. In terms of look-and-feel it is way closer to Escape Velocity than SPAZ is. Between Endless Sky and SPAZ, I honestly don't know which I would say is more fun - SPAZ has more interesting combat in my opinion, but sometimes I just want to lead a fleet of 10 warships around collecting tribute from those Free Worlds punks.
It's a little dated. That said, I have an extremely hard time playing old games, even if I have a lot of nostalgia for them. EV Nova I can play through every few years no problem.
Check some screenshots or video to see what you think. There might even be some mods to help freshen it up.