Nature magic adds to the effectiveness of your nature ability skills (your nature touch, lightning strike, etc values will increase in the skill page description) and the chance to land the dps skills. Chance to land seems to be a relationship only between the boss's evasion ability and your nature magic, although no studies have proven what the actual formula is afaik.
By "ability to hit max", I am assuming that you mean the fluctuations on the lower end will decrease and you have a higher chance to hit close to max? If so, it doesn't work that way
If you do a 5k strike and notice it only hits max of 2k on a boss, let's pretend you stack nature magic gear that increases your max skill page dmg to 6k. Your new highest hit possible would be 2/5 *6k=2.4k (so it all got multiplied by the same factor, rather than added).
Assuming no resistances, your average hit is 80% of your max. Your lowest is 60%, and your highest (obviously) is 100%. What causes people to hit much lower is resistances, and from what I can tell they basically multiply everything by a factor depending on how high the resist is. Theoretically if you're dpsing a boss that has enough resist that you'd only do 1/4 your max dmg, you can do no better than 1/4 your max dmg no matter how high your dmg value is. If your skill page says 4k the most you'd see is 1k. If your skill page is 40k the most you'd see is 10k. So with this example, your highest possible hit (on this theoretical boss) would go up by 427/4=107 using the silverweb ring. The only way to increase this percentage (say, make your 4k hit actually have a max value of 2k instead of 1k) you'd have to decrease the boss magic resist using lures.
So to answer your question, neither ring does anything out of the ordinary. The choice is up to you to decide whether you want to increase your skill page dmg by 437 and have 9 extra skill points, or increase by 100 and add ability to inflict. Personally I'd choose the latter because it also increases your vines, swarm, storm, etc which comprise a lot of dps; unless the 9 skill points would come in more useful.
Lemme know if this helps, or if I said anything that's completely wrong lol
Level 220 mage- InnerCircle of Rhiannon
Necro, proteus, unox kills http://www.celticheroes.net/profile.php?hero=runvs