As you are in your third year, I would say, almost certainly, it is better to complete it even if you decided now that it isn't for you - to ensure maximum value of time. Yes it means another not so enjoyable year - but then it will mean the last 2 years haven't essentially been wasted.
I think there is a higher chance of regretting quitting now, than regretting completing the degree (providing you successfully complete it of course).