Steffen, when I'm photographing indoor flower shows I use the SB800 for the wider shots and the R1C1 for the macro shots. Getting in so close for the macro shots with the SB800 gives too harsh a shadow, even with a diffuser. The R1C1 brings the light in from both sides and softens the shadows. If I'm shooting from say 2 metres away, I'd use the SB800, but for the real close in work, the R1C1 works best for me.
The only down side I've found with the R1C1 kit is it requires 3 CR123A batteries (1 for each flash and 1 for the commander). These aren't easy to find and aren't cheap (around $20 each for rechargeables) and you only get 40 - 60 shots out of set before recharging. So I always take 2 sets with me. I wish they'd built them to take a
AA battery.
This image was taken with the R1C1 kit (2 flashes) , D70, Sigma 150 f2.8 macro lens at f11. Note how the light is even and pretty much shadow free. The 2 flashes were mounted about 150 degrees apart, slightly above the horizontal. I'm almost tempted to buy a 3rd flash to get the lighting more even still, and mount 3 flashes 120 degrees apart.
Cheers
John