I have a client, let's say, www.example.com They use a 3rd party for their site search.

Part of using this 3rd party is a requirement that all search pages exist on a subdomain search.example.com.

The 3rd party search does some really cool stuff. They provide filtering options for a given search, organize search results to show the most popular products first, and other nice things. Even better, these search.example.com pages rank well in organic search.

My question...

Would it be better to combine everything under one roof... www.example.com?

I ask because, as we know, search engines look at subdomains as separate sites. My thought is that we'd be doing a "good thing" if we could have everything under www.example.com.

The 3rd party contends that having their search results on a subdomain isn't very harmful and that trying to combine everything under one domain wouldn't yield much benefit.

The reason I feel that it would is we'd have one site with a lot of content, instead of 2 separate sites with disproportionate amounts of content.

Maybe I'm just being OCD about it...

Thoughts?