Help to buy, ISA split or ISA transfer?

[Megemerald]

I currently have an ISA with Nationwide. I want to get a Help To Buy ISA.

I've paid into my ISA this tax year (so don't think I can just open a new ISA) and have over the £1,200 mark. I'm wondering whether I should transfer over to the Halifax Help To Buy ISA, or do an ISA split where I get a Help to Buy ISA with Nationwide and keep my current one?

Does anyone know the pros and cons of both options? Obviously the interest rates are different but what else factors into it?

Thanks in advance!

[Nutria]

I don't think anyone on the forum has much knowledge in UK financial products.