Hi, I can give you my opinion as a fellow Englishman who has been to both. Please note I am not interested in diving.
I have traveled Thailand twice now. Philippines is completely overrated. The power cuts are unbearable, air con in hotels and hostels is the 1980’s sort which needs a huge hole knocked through the walls and is very expensive to get a room compared to Thailand. You have to fly everywhere and the tickets go up drastically unless you book I advance. The flights to and from Bangkok are cheaper and from then on it’s pennies. Thailand you can go via land etc. Thailand’s beaches and islands are as good if not better than any in the Philippines. The food in Philippines is vile and is pretty much all meat. The SIM card signal barely works. Both countries have ATM’s which charge a fee. The cities are much more undeveloped due to poverty. The feeling is quite unsafe compared to Thailand and the biggest of all..
Manila = worst city in Asia
Bangkok = one of the best
Philippines there is English but only in the younger generation and higher class it seems. The barrier in Thailand is worth it. There are real shops in Thailand like 7/11 with doors and prices on the shelves. Thailand is safer, cheaper, friendlier and more with the times. I would go to Thailand and gain experience and then maybe trying the Philippines as it is a lot harder to travel there! Go to Koh Phangan and you won’t want to leave.