Totally up to your business needs. Don't get me wrong, an eCommerce website is the way to go if the majority of your sales happen online and you sell thousands of dollars worth of inventory in a given month.  So let's start with some basics - eCommerce takes time and money, incorporating PayPal buttons to your site is fast and easy.  
The main thing to focus on is how much money you are generating. PayPal charges an overall percentage on all sales and they add up quickly.  Another disadvantage is your money not being available when you need it, although the PayPal debit card transfers money instantly - the majority of people prefer the money being deposited into their business checking accounts.  In addition, PayPal disputes generally land in the buyers favor regardless of the evidence you collect.

• PayPal doesn’t have any ongoing fees or long term contracts which makes it convenient.

• “Buy Now” buttons can be encoded to allow your customers to purchase an item with a fixed amount.

• Buyers may purchase multiples of the same items.

• PayPal will track inventory of these items if that is required.

• PayPal has a simple refund process should you need to do that.

• PayPal provides for the ability to have thank you pages and cancellation pages to which site visitors are routed after the successful purchase or at the cancellation of a purchase.

• PayPal provides functionality to customize your purchase screen with your logo and colors.

• “Buy Now” or a PayPal button doesn’t have shopping cart functionality, meaning customers cannot put an item in a virtual shopping basket and continue shopping.

• Every time a new item must be added, you will either need to code a new PayPal button or call your web developer add a button. While not highly complex, it involves a few steps and it may be confusing to those who don’t use it regularly.

• Consumers unfamiliar with the use of a PayPal button, may not understand that they may pay with credit cards, and are not required to have a PayPal account. You may need to explain the process or have a separate set of FAQs to help them. However, many companies now use these buttons so more are familiar with them.