In order to answer this question properly we need more details:

1) How much risk you are willing to take: If you are ready to take more risk, you can go for alt coins. Risk here means that there are also menaces of loosing lot of your investment. But this also means that you can get higher returns in less time in comparison to bitcoin.

2) How much can you wait: Based on my experience, if you can wait for 8 months or more, you will at least get double of your investment. I will always choose bitcoins over alt coins if I have the time to wait. This is because it is much more reliable.