English. Because English is my main language, and if I only play the English versions of the games, where's the logic in using the Japanese names? And if I don't like an English name, I'll just live with it, as there's no point using all English names but then using Isshu instead of Unova. But obviously before the English names are revealed, I'll have to use the Japanese names, and it'll take me a while to get used to the English names. Like, for example, after using Japanese names for the Gen V Pokemon for months, it took me a few weeks to get completely used to the English names. But now, I can't remember many of the Japanese names (like, say, I can't remember Eelektross's Japanese name).