Whenever I hand sew gloves from fabric, I use the familiar straight stitch when sewing in the fourchettes & thumb. However, this usually doesn't last long: after a short while of wear, these stitches loosen and holes form.
What sort of stitch can I use to make sure that my gloves last?
If you are making leather or cloth gloves:
Glove making is a traditional art and its artisans are highly skilled. It sounds like you are fairly experienced in glove making, but here are some tips on stitching and making gloves.
The link below shows the classic traditional method of leather glove making, using several stitching styles: http://www.couturestuff.com/vintage-sewing-books/how-to-make-gloves-by-eunice-close/how-to-make-gloves-section-1/
A more "home crafter" glove-making tutorial is: https://www.wikihow.com/Make-Leather-Gloves
Both tutorials show several stitch options, e.g, seams out or seams in, running stitches, overcast stitches, etc. To a great degree, stitch selection appears to depend as much on desired aesthetics as anything else.
I would imagine that durability of your stitching is highly dependent on the selection of the size and fiber content of your thread; the closeness of your stitching, and the correct sizing of the pattern, especially the length and width of the fingers and thumbs.