I recently tried both of the Vandoren sample packs, and I figured I might share my impressions. For background, I got back into playing a couple months ago after being away from it for about 10 years (though I played flute). Just before this little pandemic situation started, I got my horn fixed and got a new mouthpiece. Lots of time to play and today my lips are a bit out of shape so I'm taking a break.
My equipment is a Yamaha yas-62 alto sax, a D'Addario Select Jazz D6M, and a Rovner mkIII ligature. My old mouthpiece is an Otto Link STM 6*, and I tested most of the reeds on that as well. A few I worked on with a reedgeek (beyond flattening the table), and that I will note. I have been playing standards like "Willow Weep for Me" but also jazz standards like "Maiden Voyage", with a backing track or on their own.
All reeds were 2.5 strength.
Blue Box - I used these as my main reeds back in the day, but in comparing with the others I found them a little stuffy. They don't stand out anywhere, and they are a bit stiff. I found them a bit looser on the bottom than I remembered (hard to get clean low notes), but still feels like the sound is weak on top. Maybe need to be worked over with a reed tool.
Java Red - I found these to have a bit of jazzy buzz in comparison. I really like these. They sound good on both the Select Jazz and Otto Link. They played more evenly throughout the range.
Java Green - The sound is very bright but a kinda wild on intonation and tone. The 2.5 is too soft, at least for the D'Addario. When things open up I may look for a 3. I found articulation a bit soft in the lower register in particular, probably just too soft for my setup, but for more experienced players I think it would give the most flexible sound and it has a very strong punch.
ZZ - It never really worked for me. I found it a buzzy but also very airy. I may have gotten a bad reed. I worked on it with a reedgeek and got it playing pretty well but the sound just didn't seem to have a strong core with either mouthpiece.
V16 - I had tried these before and didn't like them, but on the Select Jazz they seem just right, perhaps because play like a harder reed. Very stable and even throughout, and worked so well I ordered a box. The buzz factor is there but less than the Java, and balanced by a good core.
V12 ("classical") - It was very stiff so I worked on it with the reedgeek, and it came out the most stable in intonation and tone. It has a sort of fast buzz? or sax sound that would work in classical, more colorful than the blue box without being "loose" on the bottom. A bit too resistant for me, but probably very good on a lower tip opening. Very good articulation, good tone, good on both low and high notes, but isn't quite my sound. Strong sounding, I guess is how I would put it.
V21 ("classical") - a real surprise for me. A very clear, round, smooth tone, good in all registers, good on both mouthpieces but especially on the Otto Link. The first one played fine from the package, the second one was a bit stiff until I did a little with the reedgeek. It isn't as perfectly crisp as the V12 in articulation but still is stable in intonation and plays well throughout the range. The tone it brings out appeals to me a lot.
Overall, my favorites are the V16 and V21. If you are not sure of your sound, I recommend the sample packs. The so-called "classical" reeds should NOT be overlooked if you have the option to try them. The V21 really brings out something quite pretty that I like a lot, which particularly works on a ballad, and the V12 is very strong and stable. And although I came out not liking the blue box as much, we all know people who love them and I used to play them for years.
My only nitpick would be that some reeds, like the Java green, play much softer at the same strength than others, so the sample pack will be guaranteed to have some that work for you better than others. I don't feel I can do justice to the Java green, which is just too soft in comparison, and my bias toward the V16 may have more to do with it acting almost like a 2.75 and working with the Select Jazz D6M well rather than anything else.
I also think the reedgeek is almost too powerful a tool, if you have a "bad" or "stiff" reed you can certainly make it work, even if it's not perfect. So far I haven't found a reed that I can't make decent with it. I may be shortening the life of some reeds, but I figure it evens out - I don't spend time breaking in iffy reeds, they might die earlier but the same amount of good play time results. Plus just crappy reeds I would never be happy with all become at least good.