I would recommend whatever type you get, be sure they are waterproof. You can spray silicone on, yourself, but it plugs up the pores on the leather. After talking with the sales person at a Red Wing Shoe Store, I'd recommend Mink Oil, over Silicone sprays: it breathes, without plugging the pores of the leather; it softens up your leather to the point where you might be afraid it will tear -- it won't, but it will feel that soft, for the first 24-hours after applying it... Used it on my leather chaps, and I thought they'd rip apart they were sooo soft, and waterproof. Mink Oil is actually a cream which has to be rubbed into finished leather; only sprays can be used on suedes.
WebBikeWorld.com recommends getting bike-specific boots, as they are supposedly made with heavier thread material, some even use Kevlar, which will allegedly withstand a crash, without falling apart (they have reviews, but they tend to have champagne tastes -- and budgets!). I consider that overkill, but that's just my opinion.
I just bought a set at a local DIY/everything-under-the-sun store (Mills Fleet Farm): non-steel-toed boots, mid-calf, waterproof/oil resistant, leather, with deep tread design. Mine are lace-up, and while they work, the lacing is tedious... Both going on, and coming off.
LeatherUp.com sells a variety, for a wide range of prices. Mine, from Mills Fleet Farm, were $80; my wife needed a new pair, so she got some nice Red Wing boots: $140! Prices vary -- a lot! Neither of our sets were steel toe, or even made for biking! If you feel comfortable mail ordering a pair, check out LeatherUp. Read the customer reviews, and be prepared to pay the return shipping if not satisfied. I've had good luck with their jackets -- wish I would have taken a chance on LeatherUp's zippered boots... Cheers!
1979 CB750K (sold, 2012, but not forgotten)
1983 Kawasaki 440 LTD Belt Drive (sold, 2011)
1993 Kawasaki Voyager XII