Which bed should I choose?

Now, I am going to get my boys new beds. They are both 4. But I can’t decide between bunk beds and twin beds. Bunk beds would save a lot of room, but I like twin beds. My boys would like bunk beds more. In a couple of years we are going to get them new beds, in about 6 years, when they grow out of them. The colors in theirr room are darkish blue walls, red duvet covers, and dark brown furniture. Please tell me which bed I should get for my boys and why!

Thanks!

Here are pictures of the beds I want to get:
Twin:

http://www.walmart.com/Your-Zone-Loft-Collection-Twin/ip/10928466

Bunk beds:

http://www.walmart.com/catalog/product.do?product_id=10575814

I really like both but if you are going to buy 2 of the first bed, the bunk beds would be better. They are also cute and space saving:)