I agree that as a general rule, the Czech rifles are the slickest of the M98s.  It has been my experience that there are individual exceptions here and there among the 98s.  My moderately well used, matching numbered Argentine 09 cavalry carbine by DWM is the slickest 98 I own, followed closely by a matching number Brazilian 08 long rifle made by Mauser at Oberndorf under contract to DWM, which has seen very little use and looks almost new.  Both are slicker than any of my other Mausers, including a 1935 Mauser Chilean carbine, which is like new and is one of the first 20 made (when you'd think the quality control people would be all over these things).  Of all the other Mausers in the safes, the Czechs take all the next slots for slickness.  The Argentine still surprises me; I've handled and owned various 1909s over the years, and I'd never found one that was very slick until that little carbine, which, sad to say, doesn't shoot for beans. 

I think the Argentine carbine's slickness is probably due to it being "worn in" and having been well taken care of during its service life.  I don't have a theory on the Brazilian 08's slickness - I've handled too many matching number Oberndorfs that were from new to abused in quality, and none were as slick as that 98.  Go figure.  But every Czech VZ 24, 98/30, JC light rifle, whether matching numbers or not, are all slicker than most other Mausers, which I suspect is due to metalurgy and heat treating differences when compared to the German, Yugoslavian, Polish, et al 98s. 

There are two Mauser 98 derivatives that I think are routinely slicker than the Czechs, when you can find examples that aren't abused, and those are the Mexican 1910 and the US 1903 Springfield.  I think the reason is primarily mechanical (design); both have left receiver walls that aren't cut as deeply for thumb clearance as all the other 98s are for ease of loading with stripper clips; both support the bolt more fully during operation than the other 98s do.  Larry Brace, the well known custom gunsmith from Oregon, once told me his all time favorite action to use for custom rifles was the 1910 Mexican because of how easy it operated when slicked up.  He said he'd always wanted to build a light weight 358 Winchester for elk hunting on one of them.  I hope he did that before he passed away.  I have a 9.3x62 that Larry built for me back in the early 90s on a double heat treated Springfield action and it is so smooth it almost feels effortless when you slip one from the magazine into the chamber.

So whats my favorite 98 action?  That's easy - the VZ 33 and/or the G33/40 - slick, strong, light, and long enough for many interesting cartridges.