The real advantage of bolts over levers in my opinion is price. A good Mosin nagant can be had for $60, with Mausers following at $100 and up. A good lever will cost you at least $400. Also, surplus ammo for those surplus bolts is extremely cheap, both in 8mm and 7.62x54R. 30-30 is kind of expensive, and it is the only real .30 cal you are going to see in a tube-fed lever. Note that I said tube fed.
Also, bolts are much easier to scope I am told. Levers are better for SHTF and short range stuff, while bolts are for 200m+ hunting, and the like. Bolts are more accurate, both because of the cartridges they use and because of the fact that tube-fed (again, note the tube-fed) levers cannot use pointed-tip ammo. Think about it, in a tube the sharp point of a round would be right at the end of another cartridge's back end. Not good.
I think the only advantages of a lever are a much faster rate of fire without taking your eyes off the sights and the simplicity and ease of use. A very formidable WWIII attack of the killer irradiated zombies kind of gun. Oh, and you can use your revolver ammo in your .357 lever, which is always nice
What are you going to do with this gun? That is the question everyone asks in the 'what rifle should I buy' thread. Its like a car, you buy it to fill a void, whether it be hunting, plinking, action shooting, or collecting. I wouldn't buy a sportscar to transport a family of 6 to and from school, nor would I drag race with my pimpin Honda Odyssey. Purpose is everything.
My advice? Ask questions. Lots of em. Only bolt I ever shot was a .22 single shot, and I have never actually even seen a lever action rifle. Do some research, but take it all cum grano salis.