As Troupemaster, Snarby really is the best option.

The price key may seem expensive, but it really is not, it's 450CE if you share it, which if you translate it into Cr is about 30K (at current Cr<->CE rate). Considering the price for other 5* recipe is 25K (which you don't pay for SL armors), it's 5K more, which is basically nothing (less than a FSC run).

As for doing the run itself, it's really not that hard. Since the nerfpocalypse, SL Snarby is really easy, arguably easier than FSC (the only really hard thing is that you can't farm it, therefore have no knowledge of it). If you are really concerned about succeeding the run, pay the share of an experienced person to be sure to reach the end (or even the whole key to get carried by 3 persons, but that becomes expensive).

As for other shadow armores :
- Fallen is not bad, but have a fiend penalty which is not good, especially considering shadow armor is supposed to be used against fiends
- Valkyrie have a huge fire penalty, which alone is an entire reason to not get it. If it was not for that, it would make a good armor, especially with the fiend bonus. But Snarby would still be better.
- Skelly is not bad either, but have no offensive bonus and doesn't resist fire nor shock, which are the most dangerous status
- Deadshot is a specialized gunner armor against undeads. While the gun bonus can be ignored, other than the undead bonus it has nothing outstanding. Again, if you do a shadow armor, it may as well be good against fiends, which are way more difficult than undeads. Note that Vanaduke isn't considered an Undead for damage calculation too.

Long story short : do a Snarby armor, it will serve you well.