1080P vs 1440P makes literally zero difference on a phone this size. My best friend has an S7 edge and there's zero difference. OP3 is still AMOLED though.
Samsung pay is nice, but Android pay is becoming more widely supported. Regardless, the percentage of people that actually use either is ridiculously small right now. If you do, good for you. In my experience working at Best Buy, less than 1% of customers use their phone to pay.
Camera-wise, the S7 is better in low light, otherwise they're pretty similar. Front-firing camera on the 3T is way better though, if that matters to you.
When it comes to charging, you can't beat DASH charging. Fingerprint unlock on the 3 is just about the fastest out there. The stock experience IMO is much better than the shit that is TouchWiz.
Personally, those few things combined with the ability to load custom ROMs and customize as much as I want far outweighs the other benefits of the S7.
But yeah, if you can wait perhaps the OP5 will close the gap a little more, and obviously everyone's different. I love my OP3 and my friend loves his S7E. Both fantastic phones, and you won't be disappointed either way.