There's a new study out that has found that NOACs have a 29% higher risk of ischaemic stoke than warfarin:
Apparently apixaban and dabigatran have statistically significant increased risk whereas edoxaban and rivaroxaban have increased risk but this is not significant.
However there is a lower incidence of intracranial haemorrhages and nontraumatic haemorrhages in general among patients taking NOACs.
Remarkably these results were from US hospitals where the quality of INR control is not good. With good INR control, the number of haemorrhages on warfarin is considerably reduced. There is an interesting discussion on these results on page 4.