My 4 month old daughter has an issue with sick. Consequently we have tried Tommee Tippee, Dr Browns, Avent normal, Avent gold and NUK bottles, with both the normal and the vari flow teats on the TT and Avents.
We have to have vari flow teats as her special formula milk is too thick to pass through any normal teat as the little holes are too small. Faster flow rates make no difference because the holes are the same size, there's just more of them. Variflow teats have a cross or a slit in rather than a little hole which is needed for the thick milk gets pass through.
If you are thinking of putting breastmilk or even any of the normal formula milks into a bottle then you will be fine with a normal newborn teat. You may find the vari flow ones just too fast for a tiny baby to start with. They were too fast for my daughter when she started using them at about 8 weeks, but because of the special milk we did not have a choice.
After much experimentation I use 4 Avent Gold and 2 Avent white, all with vari-flow teats. I honestly don't notice a difference between the gold and the white and there are no leaks when feeding. If you are a little clumsy with it you end up putting the lids on the bottles slightly wonky and the hole/slit in the end of the teat isn't in contact with the lid. That means you might get a bit of dripping if the bottle is rolling about in your bag. Once you've worked this out you can see if the top's not on properly and the teat is bent a bit and so you just whip the lid off and back on again. Even that explaination sounds trickier than it is. Honestly it's as easy as putting a cap back on a coke bottle straight, just look at it quickly when you've done it.
Of all the bottles I have been through Avent have been awesome. To look at them it's not obvious they will be any good, the design looks plain and even slightly dated, but actually I can not imagine using anything else ever again now I have found them.
So if you're going to use bottles then Avents are genuinely good. They're not the most expensive either. I second what others have said about buying one bottle and testing it on your child though, I wish I'd done that at the outset and I wouldn't have a full set of Tommee Tippee's cluttering up the kitchen cupboard. Then I could quite easily have bought half a dozen Dr Browns too, they DO leak.
Also, forget 4oz bottles, your baby may well want more than 4oz by a month old, so 4oz bottles are a total waste of money. I'm not even sure why they make them, they seem so very pointless when a full size (9oz) bottle is perfectly capable of being used for a 3-4oz feed.
So in short (sorry this was so long)... Use the bottles and teats you have with the steriliser and if you get on well with them get more. Don't worry about trying to be prepared in advance- all the big 24hr supermarkets sell Avent bottles (check out your local ones) so they're always available, no need to panic and get too much in to start with.