Which bag for my gear?

I have a canon 50D, 28-135mm attached, soon to be gripped, a 50 1.8, 580exii, pocket wizard flex and mini, and light stand and umbrella. Which bag would suit me, the lowepro Slingshot 100aw or the slingshot 200aw? I do plan on new gear soon (flashes and lens). I realize the umbrella and stand won't fit in the bag, maybe to strap to the side?

get the 200AW so you have more room for future purchase.

I have the Slingshot 200 and have found it to be a good bag. It is easy to get your camera out fairly quickly by swinging the sling to the front. And when I had just a body and two lenses and a flash it was adequate in size. But anymore than that and you might wish you had a bigger bag.

A few cons I have noticed. My biggest complaint is that as you add more gear you add more weight. And if you plan on doing any long days of walking on vacation or shooting an event your back will not let you forget it. Having all of that weight on one shoulder really stresses your back trying to counter the offset weight. Second, slinging the bag to the front is only quick and easy to get the camera out, trying to change a lens requires taking the bag completely off and setting it down to open the big compartment. I know taking a bag off to get out more gear isn't unusual, but with the sling you have to take it over your head and if you're wearing a hat or sunglasses or have your hair fixed you risk messing something up. Third, the divided sections in the main pocket towards the bottom side of the bag are not completely uncovered when the flap is opened all of the way so it sometimes makes getting a lens out more difficult than it should be. Not a big deal but something I've noticed.

In closing, I do like the bag for some purposes: short excursions, when I plan on mostly using one lens. But I've been researching to find a new bag for myself and I can say for sure that I will not be getting another sling. As another option for you I have seen a few back pack (two straps = happy backs) style bags with a side opening that appear to work very similar to a sling in respect to the quick draw feature.