I think a valid argument could be made for either one.  The way I see is that the cabinets are more of an "addition or improvement" and thus have a depreciable life of 27.5 years.  That said, I doubt you would ever be questioned about it if you use 7 years.

Here's the thing.

The kitchen cabinets are in fact, "a physical part of" the property. In fact, they're a physical part of the structure. They're 27.5 year property.

Also, if you sell the property you're not going to remove the kitchen cabinets and expect to get the same selling price as you would if you left the cabinets in there, now are you? Of course not. Additionally, a qualified property appraiser will without a doubt, appraise the value of the property at a lower value without the cabinet, than they would with the cabinets there.

I see this question all the time pertaining to A/C systems. For example, a Window A/C unit is expensed because it can (and sometimes will) be removed upon putting the house on the market for sale. But a central A/C unit is capitalized because if you remove it from the property before selling the property, you will without question, get a lower price for the property after removing the central A/C unit.