I have two domains www.example.com and www.example.co.uk pointing to same website. I have PR 2 on both the website. I think the two sites will get their PR based on their own incoming links ? what are the disadvantage in regard to SEO ? How can I keep both the domain but overcome the disadvantages?
Yes, PR are based on their own domains with incoming links. For me there is no harm to have 2 websites with different TLD as I can target them to different region and I'll make sure to write content on the website with keeping in mind the region. For example I might be using .com domain for English-US language and English-UK language for .co.uk domain. If I redirecting one domain to another then I might be loose traffic from one region as it will show less on different region.
if you are updating them with different contents and treating them as two different domains, no similarituies then its ok,otherwise in 'G' eye you are spamming.