I'm building a 3900 sf home, and have a 200 amp panel but I had some problems with the original builder, and now that I have another builder working on the house he's telling me that I should add another 200 amp panel that the existing 200amp is not enough for a house this size. Can some one give me another opinion.
Thanks

You need to do a load calculation. Have the electrical contractor do it. We have no idea of what you have or need. If everything is electric 200 may not be enough.

I moved this question to the correct Forum, Electrical & Lighting.

Builders, I am sure, do not know the proper method of sizing a service entrance, I suspect they use a "rule of thumb", use whatever size they saw in another home, or worst, guess.

To size a service, need to know the square footage of livable space, not total square footage to include unfinished basement, porches, garage, crawl space, etc.

Next need to know list of all major electric appliances and electrical ratings in amps or watts, size of any air conditioning, size of any electric heat.

With this detail, the minimum service size can be calculated.

Please call a licensed electrical contractor, have a service calculation done based on NEC Article 220.
You need to decide if you are going to have natural gas for cooking, heating and laundry or whether it will be electric... this will make a big difference to the electric service size required.
Most electrical guys I know don't give out advice on building... maybe builders should consider the same.