The first consideration is how much capital you have on hand. If you've been saving money for a few quarters and are ready to invest in an improvement to your business, buying an ATM outright may be a great option. It's a one-time purchase; you won't have to pay monthly fees, and you won't be tied to a holding company.
On the other hand, you need to research and find a model that best suits your business, and you'll have to maintain it. If your company doesn't have as much working capital, renting can be a great option. While you'll owe monthly payments, you'll have access to a good machine, maintenance options and profitability. The main concern comes down to math: You need to determine if the monthly cost to maintain the ATM outweighs the revenue it will bring in.