I have not tried the Phoenix branded ones myself but I have tried LOTS of others and here are my impressions and thoughts.
Like Stosh above, I find the top coil produce a warmer and richer flavor but they tend to run drier due to the amount of wick and need to be "topped off" more frequently so you don't burn them. The bottom coils run a bit cooler since it's in the bottom of the carto and has more
juice around it. The
juice acts as a coolant and gravity is your friend in this case. They don't need to be "topped off" as often but the flavor is a bit weaker as opposed to the top coil.
It's really a balancing act to get what you want, how you want it.
Top coil
Pro - warm vapor, strong flavor
Con - needs "topped off" more often and higher chance of running dry and burning the wick.
Bottom coil
Pro - gravity help keep it wet and
juice helps keep it cooler so less chance of burning the wick, less frequent "topping off".
Con - cooler vapor, more subtle flavors
That all said, my solution is use a variable volt device and run a bottom coil. You can tweak the volts to adjust your watts on a given resistance carto and get the vape you want right in the "sweet spot". For myself that's a 2.0 ohm XL on 4.2 volts gives me 8.82 watts which is my "sweet spot" for the juice I'm using right now. Some juices taste great at that level, others I drop back to the 4 or 5 watt range.