Looking at these 2 boats on Craigslist and both seem to be in great shape the 94 nitro is a 170tf Rick clunn edition with a 75 Mercury while the 98 astroglass is a 172 with a mercury/force 120. Which would you choose and why?

There is no question in my mind the Astro will run quicker but I would go with the Nitro for one reason. Mercury built both engines, however Force was their lower line of engines and it is almost the forgotten Red Headed Step Child.

The Nitro engine is a true Mercury OptiMax, built as normal but with a decal that also says Tracker on it. I believe you will find getting any parts you might need much easier to get from your local Merc dealer for this engine.  

What you could do, is get the serial number off the Force engine and check with your closest Merc dealer and see if you can get parts like water pump kits, tune up parts, etc. I am not referring to engine overhaul parts necessarily, just parts like I have said,and fuel pump kits, under the hood fuel lines, things that an older engine might need to be replace under normal conditions.  Around here, in MD, I rarely see a boat with a Force on it anymore. I see plenty of old Johnson/Evinrude, Mercury and Yamaha outboards still running.

By the way, I used to own a ProCraft boat back in the 90's. That boat was built in the same building as the Astro boats, by the same workers even. My wife and visited that plant too.  They were well made boats.  If that was a straight Merc hanging on it's back, I would feel VERY different. I have nothing against the Nitro, as my wife and I almost  purchased one just like it. Instead we decided to wait a few more years, save a little more cash and we purchased a 20 foot ProCraft powered by a 200 HP Merc instead.

Definitely go with the Nitro 170/Merc 75. As stated above, Force was manufactured by Mercury, but I dont think they brag about it a whole lot....The boat on the other hand is a solid rig like Fishnkamp said if it had something other than a Force.

Ok thanks for the info!! I am supposed to go Friday and try the nitro out and see how everything goes

I agree with what both have said above.  I just recently bought my first bass boat, but I spent probably around 2.5 months researching and gathering information on everything, especially the engines.  Most of the local shops in and around Kansas City all said the same thing, the Force is a lower quality engine and parts can be hard to come by, and be more expensive as well. Good luck!