Google "witch hazel corian countertop" and go to images. On the third row down, the far left and far right pictures show a corner with a 45 degree seam.

Sorry, don't know how to attach the pictures here.

Here are images of one way of joining the seams. (These may be the images canuckplayer is referring to.)
http://www.myestateofmind.com/images/blogs/032311_ww1.jpg

http://www.aamericancountertops.com/add/countertop/corian/pict/108.Witch_Hazel/108.Witch_Hazel.3.jpg

I did see a photo on a blog (sorry don't remember the name) of the seams joined the way you describe. IMO it didn't look that great.

I think if the fabricator orders extra material, the seams can be joined in a way that looks nice. Of course, it would cost you more.
Kind of like sewing with a fabric that has a pattern - you buy extra material if you want the seams to match - costs more but looks much nicer.

It seems to me that you don't have to limit yourself to the color witch hazel in your search for photos of corian seams. It might help to search for any of the colors in the Corian "Private Collection" as most/all of them have a veining pattern with movement.

machree:

Take your fabricator's suggestion. I'm sure when you see the sheets laid out in person, it will make your decision much easier.

And no second guessing, either.

Canuckplayer..thank you for your response, the 45 degree seam is what I had assumed I was getting.

MercerM..Thank you for the links and the suggestion to search under corian private collection, I found a good photo done in rosemary with the counters done as my fabricator suggested and the raised bar done with the miter seam! It was a great way to compare the choices in one photo!!

Trebruchet..wise advice indeed, I feel less harried after sleeping on it. I just wish second guessing wasn't my middle name!

Yes, do go see how it would look as the fabricator suggests. It will probably be very obvious to you then. I also have a countertop with a long linear pattern (oak butcherblock in my case), and one side of the kitchen is an L. I thought for a short time about having the direction of the pattern run the same way around the corner -- i.e. horizontal on the long run, vertical on the short run -- but as soon as I saw how it would look, I realized I wouldn't like it at all. It wouldn't be wrong; I just got a little disoriented looking at it. You might feel the opposite way, but I think you'll know when you see it.

It might be easier if your fabricator didn't give you any options at all (haha) but it's actually a good thing that he's asking.

North Carolina, thank you for your perspective. I will be looking at the sheets when they come in and seeing each layout so hopefully it will become clear to me then. I really appreciate this forum!

Don't know if it's too late for this. Thought I'd post it anyway as it may help someone else, if not you.

Anyway, I just saw a pic of a kitchen that has corian countertops (may be rain cloud) with the pattern running both horizontally and vertically as you face the countertops.
http://www.pinterest.com/pin/421227371369535662/

Hope things are moving along nicely for you!

That horizontal/vertical orientation is not as weird as I thought it would be. I always thought patterns with a lot of movement looked strange n a vertical orientation, but these do not. It might be because they are more subtle than bold.

I, too, am curious about what you chose to do.

Here are some more pictures and discussion showing both options.

Here is a link that might be useful: Vein directions and seams

I think there are a lot of things to consider including the lines of the room, the potential visibility of seams, personal taste, etc. Here is a crude mockup of how my granite will be laid out in a small kitchen with an L shaped perimeter and island (I have not shown where appliances will break up counters though):