I say GB. Focus on trade initially. Use early profits to build a strong navy. Use said navy to take and protect trade nodes. This job is made much easier by sending a relatively small land force to take the two Pirate islands in the Carribean ASAP. With good trade bring a strong navy which can bring in massive amounts of money. You'll almost certainly be at war with France and Spain. It's usually not something you can help as the AI will declare war on you eventually. So just be ready for it. Destroy their navies and use Sloops to blockade their ports. Once the ports are blockaded, they can't build any more ships, which means as far as GB is concerned, both France and Spain no longer exist. Take the Carribean islands from Spain, especially Cuba which generates a TON of trade income. Avoid land wars as much as possible. With an economy based on trade, most of your land consisting of islands, and a powerful navy, you can turtle to your heart's content.

If/when other nations declare war on you, just destroy their navies and blockade their ports with Sloops.