Jonny,
Welcome to ScubaBoard. Glad to have you here.
The most important thing about masks is that they fit your face. Since faces are pretty different, and since mask molds are made in "small, medium, large, thin, fat, etc." finding a mask that happens to fit your personal face is not necessarily an easy task.
So, it isn't a matter of "buy a ScubaPro Mask" or "I like Oceanic masks" - but its a matter of which one fits your face.
Second, you're likely getting certified through a dive shop. It would likely be considered poor form to show up for your first lesson with mask/fins/snorkel that you bought elsewhere "because some guys on the internet told me this stuff was the best". The dive shop you're certifying through wants to sell you those items, and unless you consider them to be a bunch of incompetent profit-motivated boobs (in which case why are you certifying with them?), you'll likely be better off selecting your initial equipment from the brands/stock they have in the store.
Buying stuff elsewhere and taking it to the store with you the first night is not going to start your relationship off on a nice, tolerant note.
What you may want to consider is something like this:
1. Find out who your instructor is going to be.
2. Call the store and tell your instructor you want to talk to them before the course starts.
3. Meet your instructor at the store and explain that you want their help in fitting masks. (They're going to cover this during the course anyway, but you may want some one-on-one time...)
4. Listen to what your instructor recommends.
You don't have to go with what he recommends, but to not ask before you buy stuff (and to show up the first night with stuff you bought from someone else) is guaranteed to not go over real well with your instructor.
Hope this helps!
(Hint #1: Mask manufacturers often sell the same mask to different suppliers...only thing thats different is the name on the box. Three or four different branded masks could all be made from the same mold.)
(Hint #2: You can always find something from your dive shop cheaper on the internet. Buying it from the internet is not always the best option. There may be benefits to buying stuff from your dive shop at slightly higher prices. Key words: "May" be...; and "slightly". If you search ScubaBoard you will find many threads on this topic. Search button is 4th from the right, at the top of this thread.)
Regards,
Doc