When we teach bowl turning (have to do this tonight) we suggest a 1/2" bowl gouge. I am partial to P&N, but just find one you like and keep using it. The Benjamin's Best bowl gouges have flutes that are too shallow, and I personally think they should be avoided.
You can put an Irish/fingernail grind on any decent bowl gouge, use a Wolverine or some other jig so that you can maintain a consistant grind, this makes a remakable difference. Wing size is a personal choice, I like my wings rather compact. I was a long wing guy and found that shorter wings worked better for me. Once again find what works for you, there are plenty of pros out there and they all use slightly different grinds. Don't change your grind willy nilly, choose one and unless it really doesn't work for you stay with it until you have the basic cuts down. Then modify your grind slowly as you try to find what works for you.
If you already have a grinding jig and have access to a tool with a grind you like don't waste you money buying a tool with a fingernail grind on it already. Set your jig to mimic the grind and you can grind a regular bowl gouge to match it and save several dollars. I also recommend that you buy two bowl gouges of the same brand, it is nice to have a sharp one at hand when you are ready for the final passes without the interuption of sharpening in between.
Also you may want to consider using scrapers for much of your bowl work, you will find they work amazingly well and can allow you to make a bowl faster than a bowl gouge.
If you can take a class or find a mentor do it, it will make the learning process much easier. If these are not options buy or rent a good video.