New Kitchenaid mixer for a bride-to-be who loves to cook?

Thank you all for taking the time to help me out. You've given me a lot to consider. I think my next step will be to visit a store that has the 7-quart KA in stock so I can get a sense of just how big it is. As for color, Greenstuff, my niece wanted candy apple red but has had second thoughts now that she realizes the mixer will last through many changes of kitchen decor! I will be sure to include some favorite recipes, AJ -- a great suggestion! And kimhw, I also have two bowls, very helpful and a good idea for gifting. Thanks to all you Food52 picklers for sharing your thoughts so generously and for your commitment to good cooking. (btw, I am awed by those of you with multiple KA mixers!)

I think the CostCo models are specially made for CostCo and has metal gears instead of the plastic gears on mass market Kitchenaids. This was true about 10 years ago--I don't know if it hold true today.

Okay, I'll go with the crowd...I confess that I have the 5 and would like another bowl more than I'd like a bigger bowl.

But don't lose track of the most important question: what color?? (Note: That was a joke. I do know that the mixer will last longer than any color fad. But still...)

Buy her the 5 and buy her and extra bowl with lid. If she wants to bake large batches she can use the extra bowl. I especially like having my extra bowl so I don't have to wash right after making dough and before I can start my icing.
Or if you only bake half you put the cover on and refrigerate until tomorrow.

I have 3: all 5-quarts. I had several 6-quarts in a past job, and wasn't convinced they were worth the additional dollars. Too, they received many negative reviews. My sister had one on which the seal between the head and rotor attachment failed, and had a devil of a time getting it replaced. Soon thereafter, KitchenAid seemed to abandon it and come out with the 7-quart. The 5-quart has been the workhorse of the line for many years, and the one I would stick with.

I researched this topic thoroughly about 6 months ago and based on a lot of product reviews and forum discussion on the topic, concluded that the Cuisinart stand mixer performs better on tough, motor-burning jobs than the current KitchenAids. So I bought the 5 quart model because my kitchen is tiny (I actually keep it on a small counter in an alcove off the kitchen) and I really don't need the larger size. I love it. (I too made several batches of marshmallows during the holidays. Such great fun!!) You must, by the way, give this dear young woman a dozen of your favorite recipes, along with this nice gift. ;o)

Since she already knows about the gift and wants it, I'd say she's already committed to having a piece of bulky, heavy equipment in her life. No need to save a little bit by going a little smaller. I'd agree with your instincts to get the best available and go for the big one.

I have both the 6 and 7 quart and both are fantastic. I love the larger capacity, especially when I am making bread dough. Either are great but I think the larger capacity would be a thoughtful and wonderful gift.

Do you have an option to buy from a place that has both models? That would allow your niece to exchange in case she prefers the other one. Both are great and in either case she will be very happy!

Is she going to be using it to cook for large groups, or just a small family ? No point going oversize if you don't need to - and newlyweds don't usually have a large house with storage space.

I have both the quart that has worked very faithfully for over 20 years, and recently bought the 7 quart "just cause". I've had the new one for not quite a year, have put it through some good use (like making lots of marshmallows over the holidays -- which have to whip at high speed for 15+ minutes) and am very pleased. Both have the same speed range, and the only substantial difference that I've found is the bowl size. I think you niece is a lucky girl, and would advise that you can't go wrong either way. :)