Check with your accountant, but leasing usually gives you 100% write-off ability of the payments made. You're writing off a monthly business expense, and not the depreciation of the item. That's why most company vehicles are leased and not purchased, as an example. There are typically 3 different end of lease options: FMV (Fair Market Value), 10%, and $1. Depending on the item being leased, each EOL option has advantages and disadvantages. FMV usually carries the lowest monthly payment, and $1 the highest. The FMV price can be negotiated at the end of the lease (about 90 days before it ends is when you contact them about the FMV), and there are occasions where the FMV is deemed to be $0.
Leasing could be a good way to go if you're buying an item as a business entity. Usually little to no down payment is necessary, payments can be reasonable and competitive with credit cards or traditional financing, and the tax advantage can be significant. Is it for everyone? No, not at all. But if you're buying new gear every 3-4 years, and typically are putting it on a credit card, then leasing can be a good way to go.
If I were pro photographer, it's something I'd seriously consider.
A side note on EOL terms, FMV specifically. I used to work for Canon USA in the office products division (copiers, fax machines, etc.), and we did 99% of the sales as leases. Of those, probably 90% were done with the FMV option. Of those, when the lease ended, almost all were valued at $0 or one month payment, so the buyer got to keep the machine at lease end for very little. That was with Canon's in-house leasing company - COPELCO (Canon Office Product Equipment Leasing Company).