There is no question about whether sust works. Ive read alot of neg thread about it. the bottom line is that it does work. Every newbie cycle is deca + sust. its an all around great test composite. Prop sucks for beginners b/c of the injection frequency and the pain upon injection. Sust is a little better and incorporates the positives of prop plus eth. Eth is great b/c of the effectiveness but sust incorporates the fast acting nature of the short esthers.
Listen, I love sust, all newbies will swear by it. It works and Its works great. Once you have your shit worked out and have the kick in times synched, it prob better to use eth. Until then go with the sust. You cant go wrong.
And yes the legal thing does make a diff. anytime you can get gear legit, go for it. You cant beat the price and quality when it comes from Target vs your best found internet provider.