I really don't think that there is any difference in the performance of the systems. I think what happend is SNK found ways to cut down on the costs of the systems. I have a old system (17xxx) and a newer system (250xxx). The older model is much heavier than the newer one. If you go to <a href="http://www.neogeousa.com" target="_blank">www.neogeousa.com</a> click on modifications, go down to the S-video mod or the stereo mod, and you can see see the different types of motherboards SNK used. If you are interested in moding the system, and want to do it yourself, you may want to ask the people at !Arcade! or Jeff Kurtz on these forums which system is easier to mod. I think this is about the only reason the serial number would matter. Also in theroy a newer number system would have less use, and therefore last longer.
I hope this helps.
Criterionradiohead
P.S.
I did the exact same thing you are doing with your system. I couldn't afford one back in the early 90's eitheir, and when I finally got one last year...it was worth all the wait in the world!!!
[ January 21, 2002: Message edited by: Criterionradiohead ]</p>