The benefits are that you can install a good 530 Oring chain, as for what a good Oring chain will cost, start at about $100 at a discount supplier. Anything less will be suspect in quality. DID, Tsubaki and others have totally adequate chains in the $100 range. If you spend too much more for an Xring chain you are probably in the neighborhood of diminishing returns. The good chains will show their tensile strength. With an Enfield you certainly don't need the toughest thing out there. I have 7,000 miles aon a Tsubaki oring chain and I haven't have to adjust it yet. Still the same slack as new.
The disadvantage of an 18T sprocket is that it will kill a bit of punch off the lights and will possibly cut your top speed an mph or two. More advantages are that it will raise the comfortable cruising speed about 5 mph before that vibes set in. However, with the new chain, it will smooth out the bike quite a bit, too. Didn't see much difference in the mileage between the two chains. To me, the 18T sprocket seemed more practical and user friendly. It will also reduce chain wear slights, the bigger the sprocket radius, the less the chain has to twist.
Bare