I'm installing Silestone Yokon Bianco which has a pretty consistent color. Should I ask to see the slabs? If the seams are done well, are they very noticeable?
You should select your slabs. Seams should be very hard to detect. Ask to see an example of your fabricators seam work.
I agree ... I would definitely want to see the slabs, as well as the seam work. I was also very particular about the sink cut-out. I've seen enough shoddy and uneven sink installations to know that some attention to detail there was important to me.
I had Caesarstone Buttermilk installed. It's a consistent color, so what could go wrong? One slab had several white resin fingerprint sized smears. Not covered under warranty, but the install was botched, so we went to Pentalquartz to reselect. One of their slabs had a large white resin drip that would have looked like dripped paint was left on the counter.
My first seam was near-perfect, but the second installation was even better as that installer had a better eye for color matching.