Yes, your cabinets should be symmetrical. Listen to your designer. You're paying for her expertise and she is giving you excellent advice--far better to get her advice in person than to get advice from a bunch of strangers in a Houzz forum! :) Good luck!

You're keeping both peninsulas? Do you like having the dishwasher in a corner, having to take clean dishes out, place on counter, then awkwardly reach over the peninsula to put away clean dishes in the upper cabinets? I have this set up and it annoys me to no end. But to answer your question, it looks better to have the matching double door cabinets flanking the window.

Suz, form should follow function. If you need the storage, then insist on the third cabinet. :)

Are you putting in all new cabinets? or just tweaking what you have?

I need all the cabinet space I can get but appreciate what you’re saying.

You might be amazed at how much more you can store in all-drawer base cabinets versus the style you have.

If it was my kitchen, I'd actually be tempted to put the wall back up between the cooktop and the dining room so I could have an effective exhaust hood and keep my upper cabinet storage.