White white of off white?

It all depends on what you feel more comfortable in! Try both white and ivory, compare the two, and decide which shade you love better. I personally went with ivory because white would wash me out, but everyone is different!

True white doesn’t look great on a lot of skin tones. A lot of wedding dresses don’t even come in true white because bridal ivory looks white to the naked eye. My dress was ivory but looked white.

I looked flushed and awkward in all the truly white dresses I tried on. I tried on a few ivory and I felt that it just looked dirty on me. But then I found my dress, which is champagne. I think it all kind of depends on your style, your skin tone and ultimately it's about what you think and how you feel overall!

The true white in the bottom sometimes appears almost blue-ish toned in certain lighting when contrasted with off-whites and light ivories. It usually washes out pale people.

Most dresses considered "ivory" look like 68 or 69.

Choice of the best shade of white, ivory, cream or bone "whites" is strictly a matter of your complexion, hair color and skin color, and also the season or background where you are wearing it. Soft look, or high contrast? Different whites are often worn at once, though in the same family of whites. White as snow, or diamond white can be worn with ivory or creamy tones, with a slight yellow undertone against another slight yellowish tone, or pure white. And pure snow whites, or slightly off-white diamond whites are good with winter white, or any white with a slightly bluish or grayish undertone. While quilting, or when making wedding gowns, I never liked an off white that was on the yellowish side with one on the greying or bluih side. But either one really looks good against pure white.
Some colors labeled ivory in wedding gowns are what in paint or other fabrics would be called BONE white, a yellowish white like ivory but with a slight brown or grey too... like old bones. This is the tone a lot of people mean when they say an ivory looks "dirty" against a pure white. True ivories, only undertone is yellow, are great with white, whether in a man's shirt and woman's gown, or in a veil which is traditionally always a shade lighter or darker, than the gown, so when worn it is clear where one starts and the other ends. Much better on photos than a match, as even at a distance you can see the lines of each, not a big blob head to toe.
These are the bigger concerns, in color of which whites to choose.
The bad reputation of white- white being labeled "cheap" does not apply to the whole category of white-whites or pure whites. Just as hair of one color has slight variations in tone, which make it look like real hair, and not a dyed solid cheap wig, the cloth fibers of silks, cottons, linens, and nice high quality synthetic silky materials have slight variations in tone. Very pleasing, a sense of richness in tone, a sheen, particularly in weaves like satin. And super cheap acetates and other synthetics like cheap polyesters have no variations at all. The dye color is in the liquid plastic white goo before it is made into the thread, with no variations. So fabric made from it looks cheap, flat, harsh, toneless. And is like a bad over dyed wig or dye job on hair. It is awfully noticeable when worn against any higher quality of natural fiber fabric, or an expensive synthetic where slightly different tones we're woven together for a richer tone. Like a beautiful old porcelain or china, against a cheap plastic, this pairing of a higher quality varied tone white against a cheap toneless one, shows one to be a cut rate item. But a varied tone ivory against a varied tone white white, looks great.
So the issue is not does white white look cheap against another fabric in any color. But, have you chosen a flat no-variations-in-tone cheap synthetic that is white white, or a richer in looks and higher quality white-white with a softness in tone. Some of the most beautiful synthetic silks are made in China, but they are very expensive. And much of the super low quality flat toned synthetic white white or greyish white is sold mail order or at discount stores where you see pictures and samples done of rich materials, only to receive the cheap stuff. This has given these colors a bad rep, when it is the cheapness of the materials that is the problem.

Addition to above: the worst 1 week job I ever had in college, was a vacation 80 hour week sorting out gowns of the same model numbers by colors, in a huge wedding gown distribution warehouse. Every one some shade if white/iviry/ off white, more than 60 manufacturers who used different colors for the same named garment. I could only do a rough match. Then a true expert would look at my sorting, pull out and regrade slight variations I missed. Snowblind after 2 hours when working 14 a day. Ten years later I was staying with a relative, took a 3 day job at the warehouse, yearly inventory. Using a camera light and color sensir, under the same light, every actual gown scanned. Over 250 shades of white were numbered variations in the over 40,000 white-ish gowns done in that 3 days.
People who are overwhelmed when shopping, and can only rely on salon staff, are not a sign the bride to be is stupid it incompetent. Just that there are so many variations, and experienced people with very good color vision are the only ones who see the whole spectrum. It baffles a lit of people, how close a match do I need?