We use Jeffco (now Rhino) 1307LV almost exclusively. It is much cheaper than West, and a much better resin system. We normally buy it from ACS. The specs are essentially identical to the European MGS 285 that is widely used for composite aircraft construction in Europe, at a fraction of the cost, and more readily available.
West has let me down enough times that it is banned from my shop. One of its main shortcomings is that it will cold-inhibit. You do a layup, and the shop temp is, lets say, about 60F. Before it cures, the shop temperature may drop to the low-mid 50s F. With West system, you will get a rubbery part. You can then post-cure it at whatever temperature you like, for however long you like, and you will never get a good cross-linked epoxy cure.
I've done layups with Jeffco 1307 down to the high 40s F, and although very slow, it WILL cure, hard. And with a post-cure in the 100F range, will develop full mechanical properties. I know. I've done test coupons.
The only other epoxy resin system we regularly use is for applications where customers seem ****-bent on painting our parts black or dark red, and we need a higher T_g. For those applications, we use a PTM&W system that requires a post-cure to 175F and has a T_g of about 260F. (again verified by test coupons)