Thickness
When it comes to strength, durability, and longevity, thickness plays an important role. Every 0.5 mm of thickness added to the band increases its durability significantly. A minimum of 2mm thickness, like in the 2mm gold wedding band, is an ideal choice for a durable and comfortable fit.
A band of 1.5mm is also considered to be durable, but anything else thinner than 1.5mm will surely bend and change the shape of the band with time. This type of band feels uncomfortable, and you might need to remake the band.
Moreover, thinner bands can be preferred by you if your fingers are sensitive to having a band between them. Narrower bands offer a comfortable fit, and with a round cut on the edges, it doesn't scratch your fingers. If you are already wearing a ring, try to wear a new band of approximately the same thickness, or else one ring will overshadow the other.
Width
Just like a thick band, wider bands are less comfortable as compared to narrow bands. Apart from it, putting on wider bands is difficult if you have large knuckles; you might need to size up to get a proper fit.