Pick one and snip the other.

You should save the "best", based on your best opinion. Don't know if it really hurts a future transplant that much if the seedling is at the edge, but it bothers me too, just doesn't seem done right. My seeds tend to float around. How the heck do the nurseries get the seedlings in the middle so consistently? They transplant some seedlings into the pots they sell?

If the more centered plant looks decent, I'll leave it....decent meaning maybe it looses out to the other only by being slightly smaller, a day or two later germinating, or having a slightly bent leaf. If it looks weak, spindly, or has poor color it is snipped and the edge one is left....but sometimes the extra is transplanted if both look okay and I have an idea that both can be used later.

noki33: I have "floating around" seeds, too. I'm sure I didn't plant all 10-15 tiny snapdragon seeds all in one tiny clump :) Some nursery seeds are sown with the help of vacuum seeders, but I think most of them are potted up later...I don't know if potting up is mechanized, but large growers may well have equipment for that, too.

Pros germinate the seeds in a big flat, then transplant them one by one into cell packs as they develop their first true leaves. It's a rapid process, accomplished like an assembly line. This allows for one perfect plant per cell.....right in the middle.

One of the many jobs I held as I worked my way through Va. Tech was to do all of the transplanting for a small grower. He would lay out several packed seedling flats on a greenhouse bench and stacks of filled and watered cell flats. Stacks and stacks! My job was to transfer the seed flats into the cell flats, insert the labels, water, and place them on the benches. Happy little plants, ready to explode in growth.

I did it the same way when I had my own greenhouses later on, and even today as a hobby grower my system is a smaller version of the same process.

Yes, I saw Monty Don do it this way too and was surprised. Seemed more efficient to just sow seeds in pods or cells to begin with. He wasn’t pricking and transplanting them to anything bigger.

I am guessing my potting soil floats seeds around. I give the center one a little bonus but not much!

for myself: I'd save the bigger one, take away some soil from the far side, give the edge-plant a shove to middle and fill that now-open space with the soil from the other side. TADA! bigger plant is now in the middle.

Or remove the soil, cut it in two and replant both babies in two pots.