I Like the Cold--Least expensive nice solid Mausers to be had currently are the Czech 24-47 and the Yugo M-48. But there are others. The German k98K is the original military Mauser, and those are available occasionally, but you pay more because (hushed pause...) it's a k98. There are also some Turkish Mausers in the shops, but these are "small ring" Mausers instead of "large ring" like the k98, so they are harder to modify. There are
many other Mausers; getting to know them all is a whole sub-category of gun collecting knowledge all by itself.
All of the above are 8mm, actually 7.92x57 JS to be precise. 8mm ammo for them has just about dried up on the military surplus market, but of course commercial 8mm is to be had at any LSG store.
Another very nice military Mauser is the Swedish M-96, which you will pay a premium for because it's a Swede 96, but it is probably the most accurate of the military Mausers as issued. It is NOT 8mm, it is 6.5x55, which is a little harder to find in your LSG store but not impossible. There is zero military surplus 6.5x66 AFAIK. The M-96's were well taken care of by the Swedish military, and tend to be in relatively good condition.
The steadily increasing scarcity of WWII-era milsurp ammo is an excellent reason to look into reloading as a way to feed these rifles. (Yes, I know, "increasing scarcity" sounds like an oxymoron!
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As pointed out, the Mauser action is a very "nice" rifleman's action, while the Mosin action is simple, rugged, and foolproof. Personally, I don't like the safety of the Mosin AT ALL, and would not care to have one. I do have several Mausers.
To answer your specific questions, as to between the k98 and the Mosin:
Accuracy: Probably the k98.
Reliability: For sheer ruggness, no other firearm comes close to the Mosin. However, the k98 is perfectly reliable--just don't use it as a crowbar.
Ease of use: See note re. the Mosin safety above. There have been mentions of a rough trigger on Mosins--No personal experience. They're both military bolt actions, made to work in battlefield conditions while being shot at. So, no real difficulties with either one.
Ammo price and availability: More cheapo ammo currently available for the Mosin. Commercial ammo for either, readily to be had, for ordinary commerical ammo prices.
Now, all of the above said, you'll pay 2 or 3 times as much (or more) for the k98 as for the Mosin. Personally, I'd go with the Czech or Yugo Mauser, which will run you mebbe twice what the Mosin costs.
Good luck in your hunt for a rifle. Please keep us posted.