With such a vast variety of strings on the market it can be quite daunting to choose which set(s) to purchase and use on your guitar. Therefore I'd like to share my experience with different strings types and brands that I've used and what worked and didn't work for me.
Now I need to preface this first, what may sound good on one guitar may not sound as good on another guitar. My main guitar is a 1986 Yamaha FC-6 Flamenco Blanca guitar which I've used on all my recordings thus far. It has a Cedar top and Cypress back and sides with ebony fretboard and a mahogany neck. My back up guitar is a 1960's Levin LFL-7 Flamenco Blanca with a Spruce top and Flame Maple back and sides with an ebony fretboard.
For years I used Aquila Alabastro Superior Tension on my main guitar and was pleased with the results. The strings aren't your typical clear nylon they are Aquila's own synthetic gut material which they refer to as Nylgut. The trebles have a bright sound (brighter than standard nylon) which may be beneficial to those seeking a brighter tone. This may be useful to brightening up a darker sounding guitar which I recommend them for. But when used on my Levin LFL-7 the trebles can sound quite shrill since the guitar already has a bright tone, I think this is due to the tone wood pairing being Spruce and Maple which gives a bright tone that is focused in the upper midrange and trebles.
For this guitar I prefer sticking to plain nylon strings, in particular Hannabach 800 MT which has strong basses and balanced sounding trebles, overall a good set in my humble opinion.
One could experiment with mixing the basses from that set with their favourite trebles for even better results, but once you go down the realm of mixing sets there is no going back. I also liked that set on my main guitar which gave it a more even and round tone that was deep in the basses and sweet in the trebles.
I have experimented with fluorocarbon strings before in particular I've tried Galli Genius Carbonio GR90 HT. These provided a much brighter tone, however what is often the case with fluorocarbon strings is that the High E or 1st String is too shrill. But the 3rd String has a more desirable tone that is less "tubby" sounding compared to plain nylon which seems to be the case for most sets.
For recording (which is what I do) I advise not using fluorocarbon carbon since they tend to be too bright and too ringing in the trebles often requiring more Equalization when mixing, and the use of a low pass filter. They are better suited to live performance as they project more and have a greater balance in volume between the bass and treble strings.
When looking for a happy medium between Fluorocarbon and Plain Nylon strings I came across "Titanium" strings which are a different Nylon polymer that have a greyish appearance to them hence the name "Titanium." They are less bright than regular nylon but not as shrill as fluorocarbon. I have used these in recordings and while I did like the added brightness I found that on flamenco guitar they can be a bit shrill. Again I would use these for live performance more so than recording.
In conclusion for recording I found that for me personally a good set of plain nylon strings works best in the studio as any strange artefacts are reduced and there is no brittleness or harshness in the top end. In the future I may experiment with a mixed set that consists of a Carbon 3rd, Titanium 2nd, and Nylon 1st string, with a good set of nylon basses. Or a set with a Titanium 3rd and the rest of the strings being nylon.