I have both Firefly and MFLB, and they complement each other very well - different vapes for different times and places and reasons.
The both take some experimenting with to get the best out of them, so my first piece of advice is don't write either of them off till you've had at least a week or two getting used to the subtleties of how they work.
To get the best from both, the grinds need to be different - use a regular bud grinder for the FF and a coffee grinder for the MFLB.
The FF tastes better to me, but that doesn't mean to say the MFLB tastes bad, not at all. It's also quicker at vaping a "load", but bear in mind the MFLB takes almost twice as much by weight, partly as the trench is larger, partly due to the different grinds.
The FF also leaves less lingering odour behind, and leaves me, the user, less "smelly" than when I've used the MFLB. That being said both are much much less smelly than smoking :-)
I've tried shaking the FF loads to mix them around, this only really works for smaller loads, and I have got the most consistent results by opening the unit and stirring. This can be quite a messy process and impossible to do outside when there's any wind at all.
I use a 20mm brass pipe screen on the top of the Firefly load, which stops material getting stuck to the lid, but I still find it best to stir the load every couple of draws. This screen gets clogged up after every few loads, so I replace with a new one. On top of all this, the Firefly needs regular cleaning, whreas the only MFLB part that gets gunked up is the mouthpiece, and that still needs alot less cleaning than the Firefly.
While the Firefly will fit in a jeans pocket, it's just too heavy for that, and makes me wish I could get away with carrying a handbag / purse. The MFLB, a battery or two and the mouthpiece are light and small enough to carry in a jeans pocket, and the only reason to open the lid is to empty the load once it's been vaped, so it can be used outside in all weathers.
So my FF is my usual vape inside, and the MFLB for outside. Every now and again I mix things up, just because I can. :-)