Depends on the mode both those weapons are tuned to specific purposes and modes because of their Subs and Specials
N-Zap '89 is meant for stuff like Turf Wars and Splat Zones rather then the N-Zap '85, which is more of a Turf Wars and Tower Control (Haven't played Rainmaker yet) the N-Zap '89 is very capable in Turf Wars thanks to it's Sprinkler which enhances its coverage, and its Inkstrike which while easily recovered, is capable of being used at the end of Turf Wars to maybe shift it in your side or quickly capping Splat Zones either saving yourself from Overtime or winning it through Overtime. It's Sub, the Sprinkler can be used as a deterrent to the enemy team if positioned correctly, or it can be used to quickly cover a Zone. Putting it on the back of a Tower, while ingenious is too ineffective to consider using in Tower Control and the Inkstrike is just too easily avoided in Tower Control thanks to the parade walking through to literally annouce its arrival. Overall however, it isn't a pushover in Turf Wars and Splat Zones because of the many Ink coverage abilities it has, in Tower Control it's lacking in utility, the Sprinkler is almost useless in that mode thanks to how fast paced it can be.
N-Zap '85 has some pretty universal subs and specials, the Splat Bomb thanks to its non stickiness can be slid to an unsuspecting opponents feet. Or it can be used to quickly Ink a Splat Zone. But because of it's unsticking nature, it isn't as effective in Tower Control, because of this the Splat Bomb isn't the best but neither is the Sprinkler in Tower Control. It's special, the Echolocater has some pretty great uses, if your enemy doesn't have cold - blooded which will throw a wrench into your awareness. But assuming your enemies don't have it, it has some great uses in Turf War, Splat Zones, Tower Control and possibly Rainmaker, if you're like me and not that inclined to look down every 30 seconds to inspect the map, in which this will be the greatest weapon to you, because you don't sacrifice a sub to Point Sensor, while mimicking the Echolocater iis just too small of a radius to use, least in my experience with it. Overall the Echolocater saves it in Tower Control, it's decent in Splat Zones and Turf Wars but I'm not too certain about Rainmaker for both
Appearance wise both weapons have a good look to them, the N-Zap '85 and '89 both have a nostalgic feel to them and while I was not around when they were, they are both nice to look at. But the N-Zap '89 Orange is pretty bright, then again isn't Splatoon bright and colourful?
I use both every once in a while, I used the N-Zap '89 when it was new during Roller coasters vs Water slides and it proved it's usefulness in Turf Wars. I use the N-Zap '85 when it became available I used it for its Splat Bomb and Echolocater, which actually my Squid bum more times then a bubbler ever could. It also depends on the Wielder of the weapon, you can excel in the Gals or Splattershot series, but I see very few N-Zappers. Keep using it you beautiful snowflake (I mean that as a compliment)