The Storm is more or less the same as the X-Max. It's an OEM from the same company.
I own both the X-Max (V2 Pro) and the FM 5.0-S. I use the FM5 almost daily whereas the X-Max gets some love only on rare occasions where I need a very stealthy device. I say "very stealthy" because the FM5 looks like a USB hard drive and I put it in my gf's purse when we go to night clubs and concerts and we never had any question about it so far, meaning it's adequately stealthy when not in use. When in use the X-Max draws less attention but still will get you some comments as it looks like a fat cigar compared to your average e-cig.
The X-Max single cell capacity is shit poor, nearly half of the FM5 which has two large cells. The FM5 heats faster because it can output more watts, thanks to its dual cells. The X-Max can be charged via USB on the other hand, it's handy. And you can swap cells if needed, so its capacity might not be important for you.
I dislike the X-Max silicone mouthpiece and much prefer the FM5 glass one, but my X-Max was a pre-release unit and newer versions (including the Storm) sport glass mouthpieces too. So that's a draw. On the other hand and that's the deal breaker for me, the X-Max vapor path is way too short and the output is super hot and harsh. The taste is spoiled pretty fast, whatever the starting temperature, and it becomes super bland in no time. It's unfortunately the case in all the pen-style vapes I've tested so far, there's no room for vapor cooling.
There hasn't been a single occurrence where I said to myself "hmmm this is yummy" when using my X-Max. In fact it has one of the worst taste of all my devices. I don't know if the Herbstick Deluxe is worse or not but both are close, and this says a lot.
The FM5-S taste is not brilliant on the other hand, but that's due to another reason: the low "blue" temperature is way too high to start with, at 195°C. It produces good vapor but it roasts the load too fast and the taste deteriorates. Note that the FM5 single temp is even worse as it's only 210°C!
The X-Max has more temperature settings but the last 3 are barely usable: the vapor gets way too hot and the device shell becomes uncomfortable to hold after 5 minutes of use (a single timer session)
The FM5 has a larger bowl and can do longer sessions, around 20-25 minutes. The X-Max is more 10-15 minutes. Afterwards its body shell gets too hot anyways, it's bad for the battery.
Build quality is good on both units. The button on my X-Max is a pain but this has been supposedly fixed since. That's all I can think of for now. If you have more specific questions, feel free to ask.
