You'll probably get varying opinions, but for whatever my .02 is worth, bigger is definitely better for your fermenter...if you use a 6 or 6 1/2 gal carboy, you generally don't need a blowoff tube at all (assuming you don't overpitch if re-using yeast). A 7 gal or larger bucket for fermentation also effectively eliminates the need for any kind of blowoff setup (I mean, why waste any of the beer you're making!).
I use a 7 gal acid carboy I picked up around 25 years ago and never use a blowoff tube. For the first two days I don't even use an airlock, just a piece of foil.
Bigger is certainly better for a kettle too. If brewing is something you think you'll continue to pursue, go for a 10 or 15 gallon one so you can do full wort boils...it's optional for extract brewing but will improve the results. Once you move on to all-grain (and you likely will, when it becomes clear how expensive extract brewing can be) you'll be good to go, and only have to buy a few more things to go all grain.