It seems that there are two major kinds of decisions about wedding-related matters: the major and the minor. The minor decisions are the ones that only impact the actual wedding day - things like the color scheme, the precise food items to be had at the reception, the time of day at which to hold the ceremony, and so forth. These kinds of decisions don't have much to do with anything besides small, individual quirks of preference. When dealing with these sorts of issues, the goal is to keep them minor and not have a huge blowup over whether there will be a chocolate or vanilla groom's cake.
In contrast, the major decisions are those that impact your life far beyond the actual ceremony, the kinds of decisions that will clarify where your fundamental values lie as a couple. For instance, take the wedding budget. Your initial individual impressions on this question provide valuable information about the way each of you approach money and financing large purchases. Are you the sort of person who doesn't care how much things cost - you just want the best celebration you can have? or do you prefer to stay within a limited budget as much as possible so that you have money left over for other things and/or want to stay out of debt as much as possible? or are you someone who wants a balance between having your dream ceremony and keeping it frugal? And if you don't have the same initial expectations, can you reach a compromise with which both of you can live? If you can't find common ground here, it may be an harbinger of money fights to come throughout your marriage.
Similarly, the size and composition of the guest list is another issue that brings to the forefront the structure of your families and friendships, along with their importance to each of you. Little Spoon and I have had disagreements on this issue, as I come from a tiny family - I grew up with me, myself, and my parents. My extended family (by which I mean aunts/uncles, grandparents, and first cousins) were people I saw once or twice a year growing up and haven't seen much since graduating high school. In contrast, Little Spoon grew up with a humongous family whose presence was known every Sunday afternoon at family dinners. She's stayed close with them through the years and still goes to multiple annual family gatherings. We had to work out a satisfying guest list that would let me feel like my family and friends have a presence while still honoring the depth of relationships she shares with her family. This issue took many months of discussion, compromise, and back-and-forth with parents before coming to a solution that pleased us both; it also highlighted issues surrounding family and its structure that will be considerations for us for decades.
There are other such issues that can crop up and can clarify some of the values you each bring to the relationship: the sort of venue you choose for your wedding (religious? non-religious? close to home? destination wedding? elopement?), the allocation of money to various components of the ceremony and reception (e.g., photography, venue, reception food and drink, dress and tuxedo, invitations, flowers), the size and composition of the wedding party, and other such issues can all reveal places where your values are in harmony or in contrast. Planning a wedding can be a stressful process, in large part because the decisions you make about certain aspects of the event reflect values with which you'll have to deal throughout your marriage.