I say double blind testing is in order. There was a recent article from a coffee tradeshow that seemed to indicate the conical was the crowd favorite.
Honestly, without a double blind test, we're all subject to our biases and influences. I would venture that in double blind testing, even experts would not be able to reliably identify either burr type by simply tasting the resulting beverage.
There have been any number of trendy notions on the 'net over the last decade that I've been seriously making espresso, most have come and gone and few have really stood the test of time.
I have certainly been able to prepare very light and "scandanavian" roasts on a number of occasions with no difficulty at all with the Monolith Conical and the LMLM.
We spend way more time dinking around over equipment than we do coffee - curiously being that coffee is the most important part of the whole process.
If anyone can point at a bean that can only be ground and served from a flat grinder and not a conical grinder, please point me at it.