There is a difference but it’s a long story. If your talking about the same type of seeds, say Kent for example, the larger seed would have more stored energy compared to a smaller seed so you would expect the larger seed to grow with a bit more vigor. In this scenario, Kent is a monoembryonic mango variety don’t the fruit is the result of cross pollination or it was selfed( it was pollinated by itself) .
In either case, there would be a re arrangement of the genetic material and sibling seedling trees would all be slightly different on the genetic level and although they are all Kent seedlings, the re arrangement of the genetic material may have given one seedling a genetic advantage in terms of growth. In actual practice however, I have planted hundred of Kent seedlings and the majority of the seedlings grew at a similar rate.
When talking about Polyembryonic mango varieties, let’s use Sweet Tart for example, I have noticed that the larger segments of the seed grew larger seedlings at a faster rate. I’ve had some very small segments of seed like a fingernail sized piece of seed sprout and it grew noticeably slower than its larger segmented siblings.
When you compare Monoembryonic to Polyembryonic seed sizes, it depends on the varieties and at which stage of growth you are talking about. Let’s compare Kent to NDM.
Kent is a much larger seed because NDM usually has a very small and thin seed. Upon sprouting, the Kent seedling is noticeably larger and thicker in girth. Kent is great for stone or epicotyl grafting because of this fact. NDM starts out much thinner in girth and not as tall in the first few weeks or months but after it reaches a certain size, it just growth with extreme vigor and eventually outgrows the Kent.
These are my observations in my back yard in my climate with my specific soil conditions so others may have a completely different observation. I’ve grown many mango seedlings but take this info with a grain of salt and best thing for you is to test it out yourself.
Simon