My experiences as follows :
1. Hirsch. Decent quality for the price. Relatively affordable, many colour, material and texture choices. The lifetime is not too good though. After 1-2 years usually broken on the spring bar position, the keeper and loop.

2. JPM (jean paul menicucci) : very good quality. Beautiful color, thick, durable. But limited choices of colour and size.

3. ABP Paris. Quite pricey but very good quality on the alligator strap. Thick, deep colour. But for the calf strap is a bit let down. The surface is easily scratched and peeling. The colour is easily fade after 1 year.
4. Lugs paris (lugs.shop). Soft, pliable, beautiful texture and color although limited choices. Durable with calf lining underside.

5. Delugs singapore. Good quality, the stitch is neat has calf lining underside. Pliable and soft. But not thick enough for the relatively expensive price.
6. Zealande rubber strap. This is easily one of the nest rubber strap for Omega and rolex, on par with Rubber-B but more affordable. I can't recommend enough for these, if you want a superb quality rubber for your omega and rolex. Fit perfectly to the case. Soft, durable and handsome.

With all being said, IMO if money is not an issue, i would always recommend OEM straps if you want the best quality and years of satisfaction of wearing the watch. You get what you pay for. Even if the quality is not better than the aftermarket straps, these OEM straps are specifically made for the watch, therefore the gaps to the case, the hue, the thickness, tapers, etc are perfect match for your precious watch.