I tend to have the biggest debate with brides over the color WHITE versus IVORY. Does it really matter?
Yes, it does matter!
The differences between ivory, cream or white is highly significant when it comes to the subject of wedding gowns and flowers. Ivory should not be viewed upon as another shade of white like eggshell, diamond white, off-white, cream or ecru - whatever that is! In terms of color, WHITE is stark white, pristine and mixes no shades of any other color - like pure white milk.
Let's examine gowns from one of my favorite bridal gown designers, AMSALE

photo: amsale.com White Gown
IVORY has a slight tint of yellow or cream. Cream tends toward the warm, off-white tends towards the cool. Cream tends to be palely yellow with some sand tones. Off-white tends to use grays and browns as tones.

photo: amsale.com Diamond White Gown
Most women love wearing the unsullied color called white for their wedding gown. However, a huge number of women are opting for ivory shades of wedding gowns.

photo: amsale.com Ivory Gown
As per old wives tale, white is the color for virgin brides but it holds little relevance in today’s world. Whether you want white or ivory is totally a personal choice. The ultimate decision should rest on your skin tone (warm versus cool). For example, white can show off the paleness of your skin. However, some brides believe that white can be too austere. Ivory, having a touch of cream can actually be flattering to pale complexions.

white ivory cream
The better choice for lighter skin tones is an ivory or antique white. Women with medium to dark-toned skin can often pull off a diamond white beautifully. Bright whites on darker skin tones are stunning!
Side Note: I've opted to wear white on my wedding day!
In regards to flowers, they are available in white, cream or ivory. Some flowers work well with all 3 colors, (ie., calla lilies and hydrangeas). Flowers that are available in stark white (roses, gladiolus, carnations, gardenias, paperwhites, stephanotis, stock).
Your florist can help determine what type and which shade of flower works best. In conclusin, white/cream/ivory does matter and it's important you convey the color or provide a color swatch in advance to your wedding vendors.