Best Practices

Hi Guys,

I'm looking for a bit of advice. The company I work for has merged with another. Both companies have their own Windows based domains. One company has a relatively new domain with a mix of Windows 2008 and 2012 servers, the other is an awful legacy mess that started life as a Windows 2000 domain and has only recently been raised to a 2008 functional level. Both networks have the usual spate of File Servers, Web servers, backup appliances and such. At the moment I have a trust between the domains for a management layer. My questions are:-

1. Am I better off leaving the two domains as they are and just continue as is?

2.  Or, do I bite the bullet and attempt to merge the domains, given the possible legacy horrors that we haven't found yet?

Thanks guys