I've just got this question and have decided to share on the blog when it might be helpful.   Rollei makes and made quite a variety of amazing macro lenses and accessories and there are really a lot of different options to get in close on your subjects.   They even put out a handbook that covers all of these in great detail.  If I am able to make the handbook available as a download from the shop I will do so - but in the mean time feel free to e-mail me for specific info.

Here's a run down of some of the macro tools:

• Bellows Extension - 68-268mm
• Vario Extension Tube  22-68mm (works with most bay VI lenses or those with narrow barrels)
• 9mm, 17mm, 34mm, 67,68mm Extension tubes
• Retro adapter - to use a lens in reverse with auto functions
• M39/M40 Behind the lens adapter (no longer in production AFAIK)
• X-Act2 Technical Camera + lens in electronic shutter or regular lens with lens adapter
• Use of 1.4x extender gets you higher magnification since the minimum focusing distance doesn't change

Finally getting to the specific question:  

The 90mm apo macro gets you to 2::1 without any tubes and almost reaches 1::1 with the 34mm extension.  With the 68mm tube, it can get to 1::1.24 magnification (image captured larger than life size).  

The 150apo macro gets you not nearly anywhere as close even with the 68mm tube - just to 16.9::1 actually.    If you have the bellows unit all the way extended then you can reach 1::1 with the 150apo macro.  

There are three reasons why it takes much more extension than the 90.  1) Its a true lens with no retrofocal element so just to reach infinity it needs 150mm from the film plane.  2) Its a lot longer than the 90mm so it takes extra mm of extension just to get to where the 90 was starting.  3) The 90mm apo lens has a really long travel and lots of focus ring rotation.  

If you want to get higher magnification, you can get the extension bellows and mount the 90mm on it. The bellows gives you 268mm of extension, plus you could also mount your extension tubes on the bellows or even before it to get more.    If you need really high magnification, then rollei has you covered.   Just get a m39/m40 behind the lens shutter adapter and mount and of the shorter M-componon's, Leica Photars, or Zeiss luminars on it.     You can approach microscope magnification levels this way and take images of cells on a butterfly wing and things like that.   But wait, there's more.  You could also use the retro adapter and reverse mount a lens. This gets you very high magnifcation as well.   

Scales on a dead butterfly wing that I found.

This is where it all began!  Here's a snap my wife took of me at the Rollei Factory in Braunschweig, Germany.   We were in Germany this summer on a family trip.  I had decided to upgrade my Hy6 to Mod2 specs (keeping the original body panels) and we stopped in to pick it up.  It was really wonderful to meet with Hans Hartje, his son Johannes, and Frank Will, who are all incredibly nice.  I got to see some of the custom Rollei 35's and TLR's they had on hand (very beautiful and very tempting!)  and also had a quick tour of the factory which now is located in the red brick building behind the older yellow building.  I didn't ask but I assume the yellow building is where Rollei started in the 1920's, and after my meeting, I decided to start a US dealership!  I've loved my Rollei cameras for years and taken my best pictures with them. Many of my Rollei Pals used to tease me that I should be a dealer since I knew the cameras so well and after the meeting with them it just made perfect sense to do it.    btw - I'll be posting more about the Mod2 update soon.