HI Surfcat,
Booking.com and Agoda are part of the same company( Priceline) and are going after 2 different types of customer. Booking.com offers no cancellation fees on some of their hotels. However those with limited rooms and the mostly the cheapest room, cannot be cancelled. It is interesting to see how similar both sites are now and offer the same features.
Booking.com
No need to pay upfront( you pay at the hotel. Useful if you prefer this. Downside is that you do not know the exchange rate they will use till you get to the hotel.
They have probably have the best cancellation policy of any online site.
They do not offer a points system. For 1 trip per year customers , probably fine.
Agoda.com
Interesting to see that many hotels have identical prices on both Booking.com and Agoda.com.
Customers must prepay in full at the time of booking. Suits some people, while others prefer to pat at check in.
Has a points system, like your credit card. 30 days after departure your accumulate points that can be redeemed at any hotel on the website. Useful for frequent travellers.
Agoda have now relaxed many cancellation policies on many hotels.
Tim