I don't know any thing about Diamond Cabinets but we did install Bertch Legacy cabinets in the kitchen of a condo that we owned and rented out. We were pleased with the quality,finish and price. I believe they were birch in a natural finish. The cabinets were 5 years old when we sold the condo and they still looked brand new.
Here are some pictures of the kitchen from the realtor's listing:

Diamond cabinets are great mid level line. I used to work with them regularly before I retired. There are lots of color and wood choices and they are well made. Diamond will do some distressing, but it's not exactly "custom" where you get to specify the level of distressing. If you want a custom level of distressing, and a more realistic look, you need to move to a more custom line, like Omega. Yes, you'll spend a lot more, but if the look is important to you, then it's money that you're going to have to spend. You're not going to get specifiable distressing in a mid grade line. That's an upper end cabinet requirement.

I put Bertch cabinets in several years ago and love them. I have both Legacy and one Custom piece from Bertch. Ours are QS oak and are beautiful. We thought we would have to do custom because we had a small weird space to work with but our KD was able to design our space so there were minimal fillers used.

We had a custom quote from another cabinet maker and he came in about 10% higher although Bertch was running a free upgrade to the QS when we purchased the cabs. They also gave us free hardware (pulls and knobs) which was a bonus.

Some of our priorities in cabinets included full extension drawers and Blum hardware. That's not obvious on their site and I don't think a lot of people realize they have it. After several years of heavy use (including teenage boys cooking and snacking) everything is looks and operates like new.

Bertch are pretty poplular here, partly because they are made about an hour from my house. In my case the oak was also milled locally. I don't know about the other wood species. As a side note, Omega cabs are made in the same town as Bertch. Each company is owned by brothers. Bertch originally specialized more in bath cabinets and moved on to kitchens a little later.

Thanks to skyedog and hollysprings for commenting. I just saw your posts. Right now we are heading down the Diamond path, but I just discovered their drawer heights are shorter than I expected. A friend says she can't fit all of her utensils in the standard drawer because it isn't as deep as her old cheap cabinets. I noticed the deep drawers were really only 5 5/8 deep. Egads, I can fit stock pots and stacks of sauce pans on my current roll trays. Can you comment?