It doesn't really matter where English started. American English has the exact same roots as British English. Neither one sounds anything like the English they spoke when the language first started. Both have equally evolved from the origins. Languages are about the people who speak them, not the land. Some people who spoke English went away from England. Others stayed. Neither is MORE English.

It's also not really true that Americans are more literal. The British walk on the pavement because it was PAVED. And Americans say pavement, too, but just not for that bit of paved stuff.

But neither is better than the other. If you're going to be meeting more people of one sort than the other, then learn that type!

Some things to consider:

1) American English will be more useful if you're living in the US or Canada, and British English if you're living in the UK, Ireland or the Commonwealth (minus Canada).

2) The overwhelming majority of the English speaking population lives in the US.

3) Hollywood is based on the US, so most movies and TV shows in English will use American English. However, I can't think of a single American movie or TV show that doesn't include at least one British accent.

4) There are a lot of different American and British accents. The connection between them gets a bit complicated when you look at the history. Before the US was settled by the English, there were already a variety of British accents. Most of the pilgrims who went to the US were apparently from south eastern England, and that variety of English (think Samwise Gamgee) definitely sounds closer to American English than the more well known varieties of British English. The New England part of the US also has a strong Cockney influence. Add that to 400 years of separation (plus the huge size of the North American continent).

I find that British English differs much more than American English. By that, I mean I feel like the differences between (for example) RP, Cockney, West Country, Yorkshire and Scottish English are much bigger than the differences between (again, as random examples) Texan, Californian, New York and Canadian English. The only variety of American English that strikes me as very different is Appalachian English.

The most well know form of British English is RP English, but very few people in England actually speak like that. I do however find that most Americans speak much more similarly (but not identically) to actors in movies.

5) Most importantly...

I'm a Brit so of course I'm going to say British English. My main point would be that English started in England, so...

Then again, although there are completely different words for things in both and some spelling differences (I would write 'recognise' and 'colour' whilst Chris above would write 'recognise' and 'color' (even typing them feels wrong!), the language is of course fundamentally the same. The Americans are just a lot more literal in their words for things. For example I would say 'pavement' but they would say 'sidewalk' because you actually walk at the side of the road.

Also! Another point, if you're being tutored English by an American, you'll likely end up with an American accent. Obviously that's really a big deal, but its something to consider if you're dead set on visiting England or prefer a British accent, or whatever.

In summary - I'm biased and say learn British English, but it's really your call.

Part 2:

...Most importantly, despite all the different English accents, they do not hinder communication. If you put English speakers from Los Angelis, New York, Austin, London, Sheffield, Edinburgh, Dublin, Sydney, Wellington, Toronto (etc.) in the same room, they'd all have different accents; but, unlike in other langauges, they can all understand each other perfectly and they do not need so switch to a 'standard English' to understand each other.

I don't know if the situation is the same in Spanish, but a lot of languages have dialects which are only partially unintelligible or not at all e.g. someone from Austria, someone from Switzerland and someone from Germany would 'switch' to High German to talk to each other, since they wouldn't be able to understand each other if they spoke in they're local dialects. We do not have to do this in English. At the most we might have to ask someone to slow down if they have a strong accent, and we might get confused by some words (for me, "thongs" are things you wear on your feet, "Trunks" is the name of a Dragon Ball Z character, and "I'll be rooting for you, baby" is a very inappropriate phrase to put in a Pokemon game, much to my shock as a kid), but for the most part there's no problem.