I think the Blast is easier to live with for certain things. Pretty much all the wiring is accessible through the front door. Power supply/amp is a single unit that slides out easily for service. I/O board is right there. But then other things like the speakers deteriorating, having to split the cabinet to access the speakers or coin counters properly, 2931 reliability issues, body flex causing bezel fitment and speaker grille issues, squeaky marquee, etc add up. The Blast City link kit is also arguably nicer since all connections are external.
The Naomi Universal on the other hand is much better build quality but almost everything is annoying to use. Power switch in the front door but all other controls under the control panel. Can't reach the I/O without taking off the front with 4 fragile clips 4 security screws and 2 more screws. Can't reach the monitor without taking out 4+ screws and removing the whole back cover. Almost no room through the front door for game switching.
Also, I have the River Service JAMMA harness in my New Net City but it's really not good for switching between JVS and JAMMA. It's really just for converting it to JAMMA. In my experience leaving the JAMMA harness fully connected but unused causes interference in the display and also forces it into high impedance mode, so the VGA input is washed out. The only way to fix it was to disconnect the video input from the monitor chassis, which is a pain with how the cabinet is designed. I'm tempted to cut an access hole in the monitor cover. Also it's minor but having the JAMMA harness live but unused could lead to accidental shorts since visibility through the front door is so limited.
The video problem might be addressed with the current version of the harness though. It looks like it comes with an adapter board to convert the harness connector to the cabinet's VGA cable, which would fix the interference, impedance, and need to open the back to install it.