I was going to say, based on the title of your post, that we use each equally...But when you want to know where I spend the most time, it's around the island prep sink. We do so much on the island and only pretty much pile dirty dishes in the main sink.

Prep, hands down. I hate looking directly at a wall, so the prep sink will be on one side of the island (10 x 4 1/2) and the clean-up sink on the opposite side.

Prep. And that's not what I expected when I designed the kitchen.

Thanks so far-it is helping solidify all the advice I have been getting from '1 sink' users that I will regret having the clean up sink against a wall. But I am trying to convince myself that the prep sink in the island looking out the back glass doors will make up for it!
Thanks!

I may spend more time in the prep area, but I'm watching what I'm doing more there -- I think. It seems that I can gaze out the window a bit more when I'm at the main sink. Didn't matter that much in our kitchen -- I couldn't more the main sink and the prep sink and work area are on the far side of the island and share essentially the same view.

My clean up sink is against a wall, but that wall has a focal point backsplash and glass front cabinets above that, so it's pleasant and interesting to face the wall. My dishwashers don't require rinsing, so I spend less time there. Also, the big entertainment and reunions where lots of china, silver, and crystal that cannot go into the dishwasher are used don't happen daily and usually involve more help. This is just to clarify why I end up using the clean up sink less on a day-to-day basis.

Which sink you end up spending most of your time at will most likely depend on the flow of your kitchen. Our smaller sink has the dw and is closest to the table and fridge so it's used for veggie prep, dw, and drinking water for the table. The large sink is closest to the range and coffee pot so is used during cooking (it's also where I do most of the prep) and for washing items that don't go in the dw (plastics, some pots and pans, wood, knives.) Since our kitchen is designed so that both sinks can be easily used for prep and clean up (one person at the small sink scraping plates and loading the dw, another at the large sink doing all the other clean up.) I would say we spend about equal time at both sinks. Although both are under windows, I tend to spend more time looking out the big sink window while washing by hand (I'm much more focussed when doing other tasks and rarely gaze about.)

Our kitchen isn't done yet, but I can tell what I think will be the sink usage:

I will use the prep sink probably 75% - 85% of the time

My DH will use the cleanup/main sink 75% - 85% of the time...I cook, he cleans up (kids are usually doing homework b/c of our crazy schedule!)

I have to admit though, that neither sink will face the wall...the main sink is in front of a window to the backyard; the prep sink is in the corner of the peninsula facing the DR.

In our old kitchen, the only sink faced a wall and we didn't really have a problem with it. As with Lascatx, when I'm prepping I'm watching what I'm doing rather closely since it usually involves knives or peelers. My DH, OTOH, watches TV while he does dishes. The main reason we put the sink where it is is that I loved Fothia's bay window sink and wanted to do the same in my kitchen. The other reason is that I wanted a "real" vent over my cooktop but not in the window and (1) there wasn't enough room on either side of the window to give me decent work space on both sides if I put it on either side of the window, (2) I like the more balanced/symmetrical look of the cooktop centered on the wall, and (3) there wasn't enough counter room for both on the back wall (it's what I had before and hated it!)

Prep, by far, which is in the island facing the back windows/french door to the back garden. The cleanup sink is against the wall. No regrets.

My earlier reply said these posts were solidifying the advice from 1 sink users that I would regret putting the main sink facing the wall- I meant to say that your responses are helping support our new plan which moves the main sink against the wall and the prep sink looking out the glass doors despite some of the advice off this forum we received. (obviously provided the functional design works) .
Thanks -it is helping us get close to finalizing our plan!