Multiple blog platforms

Hello. I’m thinking of trying out both WordPress and b2evolution. I’ll install b2 first and may never get around to WP, but thinking in the long term, if I would run both platforms what is the best directory structure to install into?

My first thought was to set up a subdomain “weblogs.domain.com”, but obviously only one blog install would answer to that mapping. If I use a subdomain for blogs then I only want one subdomain for both of them. I have a few thoughts on what is best, but want to hear what organizing principle you guys would use, because you’ve probably been doing these things longer than me.
Thanks.