Dating - advice needed!

So I went on a date with a guy from tinder about three weeks ago, he was nice enough and we went on a second date a week or so ago. We've chatted a bit inbetween and he's a nice guy but ultimately I don't think it's going to go anywhere. Last week he asked to meet up again and I half put him off but in the end I said I'd see him tomorrow eve.

Then last week I went on a date with a different guy I'd been chatting to and we totally hit it off and have already arranged to see each other again Tuesday. It just has that spark the other one didn't.

So...I now don't really want to go on this date tomorrow with the first guy. But I feel really bad about binning him (I'm just too nice ha!). Should I meet him tomorrow and end it, which will be more awkward face to face, or do I just text him and call tomorrow off and explain he's a nice guy but I don't see it going anywhere? To be honest I'd rather do the latter but don't know if that's really bad :/