The manufacturers have different ways of measuring and accounting for space -- like one measures to the wall and one measures to the end of a shelf. I'm told they don't necessarily reflect usable space. Even if they did, you are talking about a tiny fraction of an inch down the back or side. When you are talking about a cubic foot or less, you may well find that the one with the smaller stated size has more usable space. I think that's what you ought to look at -- how well the space looks like it will hold the things you need and make them easily available to you. You do lose a little space in the columns because you have basically one more wall -- one on each side of the fridge and the freezer (all exterior walls) as opposed to a wall on each side and one (sometimes thinner) between the fridge and freezer. I have the Thermador columns. Mine are 30 and 18. If you have the space for a 24" freezer, I'd go for it. I'm happy enough with the 18" in the kitchen, but we do have another freezer. The Thermadors are great looking, well-lit, well arranged -- love the higher bottom drawer. They are virtually silent, chill well, have a super chill that is great. I love the full-extension drawers and that the door only has to be at 90 degrees open to allow the drawers to open fully. I think the space is very well designed and utilized. I didn't like SZ's ice maker at the very bottom - not good for a tall person with a back and neck issues and Texas summers. I really like the ice drawer in the Thermador right in the center although I wasn't sure about it when I first saw it. I didn't have the option of 54", so I didn't really compare a pair of SZ 700's. They were the only SZ'z I liked and the choices I had didn't work as well for me. I can't say anything negative about Thermador though. I really love mine.

I have a 30" fully integrated refrigerator column and an 18" fully integrated freezer column, and I love them both. I would prefer a 24" freezer column but I didn't have the space. Either way, I highly recommend them. I got mine on clearance (older model) to save some money. They are virtually identical to the newer models, just without the LED lighting. It's also nice that you can install them in different places if you want to. One thing to be aware of is that the installation for the integrated (paneled) models is extremely complicated. It took my GC 3 days to get them installed. And if your ice machine ever breaks, it will cost a lot to have someone pull the freezer out for service (if they have to access the back behind the freezer), and that cost is not covered by warranty. I assume this is true for all integrated units, not just Thermador. Here is how ours look installed (all the way on the left in the photo):

yes, johnsoro25, my situation is like that, right next a little half wall but on the opposite side of the kitchen (little wall on right not left). As long as the articulating hinge allows the 90 degree opening to get everything out I don't have an issue. Though, I am a bit weary about not having the landing space exactly next to the fridge. My current design has a 24" pantry between the fridge and counter. But moving that fridge next to the counter means a really tight space in the aisle.

"I was told by the installer that the columns will not be pushed back all the way into the cavity and I should expect them to stick out 2-3 inches!" Looking at the Thermador T30IR905SP refrigerator -- of the Thermador 1383871 pair (which is what I assume you bought) -- specifications and page 10 of the installation instructions I believe the installer is incorrect. You can even skip a handle with the Thermador TFL30IR905 30" handleless door ($580 yikes!). Eighty pages of installation instructions. Poor guys.