Either one. But that is an ELL question. I prefer shorter: Imagine there is.
– LambieJan 09 '17 at 21:48
They are both OK. "Better" is not something we can answer from the question as you've posed it.
– John FeltzJan 09 '17 at 21:49
Ask John Lennon… strictly speaking 'that' is necessary but modern English speakers don't do strict, so it makes no difference
– Robbie GoodwinJan 22 '17 at 01:47