It is the difference of GTX980 being 9% (TPU) or 4% (Computerbase) faster than RX480. So looking at your statement, 5% "doesn't seem to make much difference" but 4% is "not close to". Different standards?
We can even give the 1060 a
15% performance increase over RX 480 4GB. Unless it costs $249, it's nothing special. The 1060 6GB version will likely cost $279-299. That's $80-100 better spent elsewhere. Option 1: save it towards a future 2018 $200-225 GPU upgrade. Option 2, get a faster CPU.
I'll just cut and paste what I typed in the other 1060 thread.
The mainstream PC gamer has to be very careful on this one. The extra $ spent on the 8GB RX 480 is better spent on a faster CPU instead. Move up from an i3 to an i5, from a stock i5 to an i5 K. It also doesn't matter if AMD claims that RX 480 was designed for 3-4 years in mind. It's a 2 year or less GPU. For that reason I question spending $40 more for the RX 480 8GB version. The issue with GTX1060 3GB is that for modern games that's too risky. Otoh, if GTX1060 6GB is $279.99, that's an $80 difference between that card and the $199 RX 480 4GB. We would then come full circle again and I'd recommend the mainstream/performance gamer spend the extra $80 towards a faster CPU that will last 5 years. No one had an issue recommending 3.5GB 970, 4GB 290/290X/980 for all of last year so there is no particular reason to even go for a 6-8GB card for this performance class over an 4GB card for 1080p gaming.
As you said though, the NV brand name will ensure they will be able to sell VRAM gimped 1060 3GB over RX 480 4GB. The hilarious part is that NV PR/marketing will not be able to use that 4GB is insufficient for 1080p gaming against a GTX1060 6GB but then still be able to recommend GTX1060 3GB over the RX 480 4GB. For that reason, AIB RX 480 4GB will likely be the best mainstream card in 2016 as long as AIBs can hit $210-220 prices.
Knowing NV though having a $239-249 GTX1060 6GB creates too large of a gap with the 1070, unless they later introduce the GTX1060Ti. I am thinking they will price it much closer to $279-299 than $239-249.
$199 RX 480 4GB
vs.
$299 GTX1060 6GB = 50% more expensive
$279 GTX1060 6GB = 40% more expensive
$249 GTX1060 6GB = 25% more expensive
In all of these cases, the GTX1060 6GB is a worse price/performance card.
In summary: The budget/performance gamer will be way better off either putting the extra savings towards a next generation 2018 GPU upgrade
if GTX1060 costs $279-299 ($80-100 is a LOT of $ towards a next gen 2018 $200-225 RX 480 successor that would make the upgrade just $120-145) OR putting it towards a faster CPU for longevity. Unless the GTX1060 6GB costs $249, RX 480 4GB will be the best value at
$199 among all of these cards. The extra 10-15% performance isn't going to matter over 2 years but moving from an i3 to an i5, or i5 to i5K is $ well spent. If GTX1060 6GB costs $279-299, then we'd looking at moving from an i5 6600K to an i7 6700/K for a new system build/platform upgrade. In that case, it's not even a contest in favour of the i7 6700K + RX 480 4GB >>>>>> i5 6600K + GTX 1060 6GB.
We've already seen that cards like GTX760/960/285/380 (and their predecessors such as HD6850/GTX460/HD7850) are good cards for 2 years but not much more. It's forward thinking for a mainstream/performance gamer to consider buying a $200 card vs. a $270-300 card, but then selling the $200 card and buying a new card in 2 years and guess what? You have $70-100 extra to upgrade since you never bothered wasting it on just 10-15% more performance. That's smart upgrading on a budget. Same reason I recommended R9 290 over the GTX960/280X as it worked in reverse. Spend a little more and not worry about upgrading to the RX 480/1060 in the first place.
I even said for almost all of 2015 that GTX960 users will spend $200 on that turd and then another $200+ on a GTX1060 to upgrade to get a card barely faster than an $250-275 R9 290 OC that they could have been using since November 2014. On this forum there is a tendency to downplay price/performance and reinvesting the savings towards a future upgrade card -- this is because this strategy destroys the attractiveness of
many NV cards. It's one thing to spend $80 more at the high-end for bragging rights but it's pretty illogical to spend $80 more from a $199 card for 15% more performance when that $80 can be used towards a future card priced at $200-225 that will be 30-60% faster than the GTX1060/RX 480.
In fact, in 1 year we went from $649 GTX980Ti -> $399 GTX980Ti and in less than 2 years we went from a $550 GTX980 to $280 GTX980. With how quickly GPUs depreciate/drop in value, it's not wise to overspend too much $ for what a 10-15% increase?
It's also appalling seeing NV supporters pushing what is likely to be a $250+ GTX1060 6GB so hard against the $200 RX 480, but R9 290 was $280 and was as fast as GTX960 SLI, and yet they ignored that card. Back then spending extra for 50-60% more performance wasn't worthwhile but now spending $50-70 for what a 15% increase is worth it? Complete lack of objectivity detected. The equivalent to that performance comparison today would be a $279 GTX1060 6GB ending up as fast as $400 RX 480 4GB CF.