Certainly better to take new cards from three-year warranty, I think card Rx series is the best choice now!
R9 vs. Rx has it's pros and cons,
RX
-lower power consumption
-One 6 or 8pin connector
-higher resale value
(CONS)
-slightly scaled back hashrates, especially at stock bios (modding the bios voids warranty)
-expensive
R9/HD 7000
-higher hashrate
-high bus width (384 and 512 depending model)
-generally less expensive
-fantastic if you have free electricity.
(CONS)
-harder to source
-likely less support and optimization moving forward
-probably used (and abused) for up to 4-5 years.
-takes up as much power as a stovetop
-hot as a stovetop
-as heavy as a stovetop
-not a stovetop.
So much wrong in this post.
R9/HD 7000
- Better price per hash
- Much better build quality compared to most RX series GPUs
- Never have to worry about melting SATA cables since they use max 20 Watts from PCIe slot compared to 100 Watts like the RX 480.
- Already ROI'd for most
- Use a little more power but it shouldn't make a difference since your profit is much much greater than your electricity cost anyways. If the 280x is too costly for you to run, so will be the 470 and you shouldn't be mining anyways due to your electricity costs. The difference is maybe 5cents daily on 10c/kwh power.
- End of depreciation curve. Pretty much won't depreciate 50% like the RX series. Buy today, mine, and sell in 1 year for almost same price.
- Much more stable AMD drivers. When a GPU hangs, it doesn't freeze your entire system or BSOD.
- Doesn't require HDMI Dummy plugs.
- Easier to use in Linux due to temp management
- No stupid RGB LEDs which are crazy annoying at night and pose a security risk.
- Southern Islands Architecture is more geared towards GPU Compute rather than Polaris which is more geared towards gaming and VR.
Only con I can think of is due to the Tahiti's bad speed in ETH. Hawaii is still fine.
... waiting for version 9 ... 10 ... 
