The biggest benefit of having your own snorkelling equipment is fit. You don't want a mask that leaks or creates undue pressure on your face...just like you don't want fins that will give you blisters. IMHO...buy local...or make sure you can exchange equipment bought online.
Skin and scuba diving are the greatest things since sliced bread. Don't goof it up with subpar equipment.
I agree with Jim above. The best mask is one that fits your face especially if you wear glasses or contacts. Contact your local dive place. We got ours from our local dive shop and they even had a pool where they suggest you try out the equipment to see if the mask was fit right. We probably paid alittle more but the masks were great and still functioning 2 years later.
I picked up several cheap sets of snorkel gear in the middle of winter at Sam's Club one year. We've been using the gear for several years now with no problems. Plan to use it on our upcoming cruise in April as well! I think if you are just a beginning snorkeler and aren't sure it's going to be an ongoing hobby, you are just as well starting off with an inexpensive set. Work your way up to the "better" stuff if you decide it's something you're going to do often enough to warrant the expense. We love snorkeling and had intended to replace our cheap stuff with better quality as soon as it starts failing us.......but so far, so good.