Vinyl gutters are good the issue with them is making sure you use 100% silicone to seal end caps and seams. We have used the extensively with making giant banana splits, ice-cream sundaes etc. There are also pvc as well as vinyl gutters both are UV stabilized and food safe.
I've looked at the NFT tubes for sale at a local hydroponics store, and theres no outward differences from what I see.
I've been using rain gutters and PVC tubing for NFT for a few years.....and have seen commercial systems set up using them as well.so my best guess is, that your good to go