It depends on the capacity you need. If you MUST have the extra room, saddlebags (or "panniers" on a sportbike) will do, but I think they're more of a pain to remove. I have a big expandable tankbag that I use.
I've got a tankbag that I used for the first time on a long ride a couple weeks ago...the bag is great, but the one disadvantage is that you can't tuck in under the windscreen (at least not an R6 windscreen) with the bag in the way. It gets to be a pain after you've been cruising down the highway at 80 mph for 100 miles straight and feeling the full windblast the whole time.
Overall though, a tankbag is a great way to carry a couple days worth of clothes and stuff you need for a weekend.
Had a nice tankbag, but sold it after the first use (long trip) because it is way too obtrusive (gets in the way) when you want to change positions, e.g. tuck, lay on the tank, etc. I now have a Rocket Locker (tailbag) and never take it off (big enough to hold a weekends worth of stuff, but not large enough to be bulky when empty.
you get used to the tank bag being up front. takes about 3 rides, then you won't notice it at all. I have a Held tank bag the I can strap to the tank or to the rear seat if I want to. it always stays on the tank.
I too would prefer a tank bag. However, I ride an FZ6 and most decent sized tank bags are up in your face due to the tank design in this bike. I felt like it was going to choke me. So, I am looking at some Givi hard cases which are really nice even though these things take away the "sporty" look. ALthough, there are some really nice, and sport looking saddle bags. For example, Tour Master has a "Sport Tail/Saddle" bag combo in many colors. There are others but I have to look up the names. Just my 2 cents worth.
I use my tank bag when I just need to carry around random odds and ends. A little more and I grab the tail bag to complement the tank bag, or to just use instead. I'll be purchasing a pair of saddle bags sometime very soon... because I'll want the storage for longer trips, can't store a weeks worth of stuff in just a tank bag.
If you don't commute on your bike or do any long distance riding a decent tank bag is probably all you need. I just ordered a Tour Master Cortech Mini tank bag and it's perfect... big enough to carry the basic supplies but not so big that it gets in the way.