How should i go for it?

I have 2 sites
site B is redirected into site A now (site B is easy to remeber name)

Site A is around 5 years old with around 50,000 pages indexed in google and Site B has around 15000 pages indexed
both have PR of 3

All files are in site A now and site B just redirects…
Site A is ranked well for many keywords…

Now i want to launch a new design of the site but

Now i want to move all the files to site A to site B (now the site should run from site B)
and use site A as redirector with out losing serp rankings and traffic…

i know uploading all new files to site B and 301 redirecting the whole request of site A to site B may be one idea…
but can there be any problems in doing so…?

should i leave site A as it is and launch new site in site B
That way ,site A traffic and serp may not be lost but there might be content duplication problem
and in long run it may create name branding as well

so how should i go about it any suggestions?

Try Google’s recommendations.

I think you should redirect the website A to website B… Because some times managing two sites becomes difficult. Moreover, with redirection your are passing on the reputation of website A to website B.

You must read this Google’s help blog post…

As long as every current URL is set to redirect (301) to the relevant new URL, it shouldn’t make any difference to SEO or users which domain you use.

If by

301 redirecting the whole request of site A to site B may be one idea
you mean redirecting every request on site A to the homepage on site B, that is a really really bad idea. Not only will it hammer your SEO, when Google finds that pages no longer have the content on that it expected them to, but it’s a sure-fire way to lose most of your visitors, for exactly the same reason.

If I go to an ‘inner’ page on a website and get redirected to the home page or to a generic page that says “we’ve reorganised our site but we’re too lazy to put redirects in place so you’ll just have to find your own way round, sucker” (OK, they don’t usually have quite that level of attitude, but you know they’re thinking it), I’m outta there before you can blink, and I won’t go back.

I started a thread about this recently, should have some relevant information in it:

Thanks for comments
and also to all other commenters above.

I mean one on one page redirect(not a blanket site redirect or not redirecting to homepage of site b).
for eg,(I am using mod rewrite now) gets 301 redirected to with permanantely moved message

for now, i am thinking of testing things with the less popular folder(section) of site a
and then test with the keywords for site B(if it gets ranked for earlier term)
and then proceed accordingly.

I am thinking of having
and popular section of for now
and redirect all less popular areas and work on optimization of site b

thanks for comments and keep the thoughts coming