What is the real difference between custom fabricated granite counter tops and pre-fabricated granite tops?
There is no difference in quality between the pre-fab and the custom if you get the same type of granite . Custom fabrication is more expensive for a few reasons.
1. Custom color - a color that is not something that is sold all the time and they may have to purchase it from a different supplier.
2. Edge - Some come with different cuts on the edge. The more difficult the cut the more it will cost.
3. Fit your needs - They will come and measure your kitchen/bathroom and make the countertop exactly to YOUR specifications.
If there is a pre-fab piece that exactly fits in your space then I would buy that. Chances are that will not happen. I would recommend getting the custom granite for the best look in your house.
Kitchens generally need custom granite tops as the cabinet configuration varies from kitchen to kitchen.
If you want to save money you can consider granite tile with tight grout lines. It's still pretty, but not as easy to maintain. You may also consider doing the solid surface granite as planned, but choose a coordinating tile backsplash.
Since you are remodeling, you can find out specific dimensions of pre-fab granite and see if you can lay your cabinets out accordingly. You may find, though, that this doesn't allow you to really get the kitchen you want.
If you have any small areas that need granite, you can ask about leftover pieces from other jobs.
First of all do not use the term *pre-fab. You just mean slabs of granite you purchased from a supplier which you then will need the installer to cut/seam and place on your cabinets.
You will have a front exposed edge.
If you purchase granite from one supplier and ask an installer to put it in - you are providing an opportunity for one to blame the other should a problem come up.
You need to contract out to (1) source to come out and measure for the top, fabricate the top by grinding your choice of edge on the front, cutting for the sink/ possibly drilling for faucets/backsplash and installation. This way if there is a problem you have only (1) contact and they are the responsible party.
This is the only way to do this.
A good granite company will have no trouble doing any of these things. Any seams should almost disappear when the correct filler and polishing is completed. All you need to do is provide them the brand and model number of the sink you are using. They can undermount this for you.
Get a couple of prices in writing with an exact amount stated for the entire job - including removal of the existing top to a complete install of the new.