gtx 1060 6gb is the stronger card but the rx 480 performance does is not far off the 1060, so it is really up to your budget and yeah it is also important to know what your powersupply is, ir if your psu is capable of running a 1060 or a 480
if you have the budget for an i7 why not go for it. what r u gonna use it for anyway? if its just gaming the i5 4460 is the sweet spot of cheap price to good performance.
+1 for the rx 470.
but to answer your question, just get the cheapest as they will perform the same. it all comes down to looks and cooling performance.
hmm that i5 would still run even a gtx 1070.
but i would just recommend a gtx 1060 or an rx 480
and if you can upgrade your ram to 8gb, better if 16gb
and check your power supply if it is at a good tier and or its wattage is sufficient enough for your gpu upgrade.
by way your friend is bs...
just sell the two gpu and get him a 1060 or rx 480..
your proc still at tier 1 and would go toe to toe with a skylake i5-6600k.
afaik that gtx 770 still would rock at 1080p. it is as good as a gtx 1050ti