XROS 4 is compatible with the entire XROS pod series.
The latest XROS pods in 0.6Ω and 0.8Ω with top filling system in 3ml capacity are also available now.
The COREX 2.0 provides the best flavor when SSS Tech prevents leakage.
For all these pods, which one is your favorite? 
All great pods and excellent flavours but for me my preference is the 0.4ohm as I use xcross pro which with a 0.4ohm pod can increase or decrease wattage to find that sweet spot in the e-liquids the 06 ohm /08ohm ect,are also great pods but only give eco norm or power on my xcross pro I like more control in my vape.
Exactly, for XROS pro, 0.4Ω can bring you a lot fun when you change the wattage~
The main reason I like control of wattage with 0.4 pod is a lot of shortfills are 70-30 mix using this mix in a pod system like xcross pro means you use higher wattage this drains battery means more charging so the trick is add your nic shots ask for 50-50 nic shots add to your shortfill 70-30 changes ratio to 60-40 means lower wattage longer times between charges increases flavour better throat hit and can adjust wattage to find that sweet spot.
Very detailed and professional explanation! 
0.8 pods are my favorite. I tried the lower ones but they felt very “airy” and I like the tighter draw.
Sure! What works best for you is the best choice. 
I like Xros3 and it got pick pocketed from me in dollar store like Wdf
Had it for years no issues
Got xros4 and not once have I had one solid pod work right or not leak or have the battery stop working and just blink, tried different tanks and ohms, same deal
Plus 2 air holes but only one works, shove a pin it it, won’t go through 2nd hole
It’s garbage for me
