Fizzy,
Glass is more expensive in AU and in the UK, but here it is fairly cheap and probably worth the extra $$ to upgrade. Plastic WILL scratch at some point, and that is just more potential for infection. Besides, clothes like that, you can afford it
Also, you gotta remember whose telling you all this. OZ has like 50 bazillion buckets fermenting at once. That many Carboys costs so much he may as well buy a unitank!!
Buckets are great here for newbies, and good for some applications, but a lot of us would recommend you upgrade to a 6.5g glass carboy for your primary. You can see into it so you know when it's fermenting and when it's not, and you won't have any problems with the seal.
Just my $0.02, and no offense to all you bucket heads and "better" bottle losers... I mean users...
Rob