Sorry if I don't say anything worth saying...
In its days (1854 to about 1869), the Whitworth rifle was the preferred rifle for long range matches in England. It comes as no surprise when Confederate agents abroad were instructed to purchase long range guns that they were told to investigate the Whitworth.
The Whitworth featured a hexagonal bore that had a 1:20 twist. It fired either a hexagonal or a cylindrical bolt. Tests showed that the Whitworth could stirke a 32 feet long by 2 feet high target at 1880 yards.
What made the Whitworth so good. First, the bullet was fitted to the bore better than any other bullet had been. Sir Joseph Whitworth had examined the Enfield and determined the reason for its inconsistent results at longer ranges was that the gun or ammo wasn't consistent. So, he set out to produce a gun whose bore was precisely made and a bullet, called a bolt, was precisely fitted. His success was proven in numerous tests against the standard Enfield and other arms. However, because the Whitworth fouled easily, it was found unsuitable as a standard infantry weapon. Numerous were issued to several regiments in small quantities though.
One thing not discussed by many is that the long, slender Whitworth bolt enjoyed a better ballistic coefficient than many of the minie balls (and its derivations) used by most armies. Long & slender beats short & fat.
The Whitworth's reign came to an end in 1869 when a breechloading Metford rifle (I think it was using Henry rifling) usurped the Whitworth at the long range matches. It is likely that because the Metford was breechloading, that a bullet could be better fitted than a muzzle loader.
Greener mentions the Henry rifle barrel was selected for incorporation in the newer British breechloader. Henry's seven groove progressive depth barrel was a success in the Martini-Henry rifle. However, he doesn't address the muzzle loader. From a glance, I've found nothing in my other contemporary works on the Henry.
Now, as to which is better. Historically you know my answer. However, bear in mind that the Whitworth really didn't have an edge over the Enfield at distances below 500 yards. While it's trajectory was flatter than the Enfield or Springfield of Civil War fame, it was at distances over 500 yards that the Whitworth's superiority became apparent.
Either rifle would be good for game but the Whitworth can be a prima donna that requires a lot of work to figure out what works good in it. I'd go with a cylindrical bolt (Lyman makes one) if I went Whitworth. Hex moulds are hard to get and very expensive.