There are other brands such as Brown Precision, MPI, Manners, High Tech Specialties and possibly others that use basically the same construction techniques and are every bit as good. But McMillan offers by far the biggest selection of styles and patterns to fit more rifle brands. More color and style options as well.
The Bell & Carlson and HS-Precision use a different, much cheaper construction method. While they can be decent stocks if they incorporate an aluminum chassis inside the fiberglass, it is the metal inserts that make them heavy and chunky feeling. B&C makes some without the metal inserts that are quite weak and easily broken.
Most of the others really need to have the rifle sent to the manufacturer or have a competent gunsmith do the final fitting. McMillan's will almost always bolt up right out of the box or maybe with some minor DIY trimming. Some glass bed the actions, but it probably isn't necessary. I've done it both ways and never noted any difference in accuracy.
It may be too late if you've placed the order but I'd highly recommend the Edge version over the standard fiberglass stock unless it is going on a magnum rifle. The Edge stocks are made from kevlar instead of fiberglass and typically run about 1/2 lb lighter. The kevlar is actually stiffer and tougher than fiberglass. The Edge stocks also come from the factory with pillars already installed. They run about $90-$100 more, but combined with lighter weight, stiffer material and pre installed pillars are well worth the extra costs.
There is about a 4 month wait, if the order has recently been placed it isn't too late to call and change.