Depends on what you're doing, generaly speaking, rank gives more success % than dex.
For high "ranked" stuff like say fine/finest leather strap for weaving. something ilke 5-10 dex will increase ur success by 1%. and If you're success is too low to start off with, you might not even see the 1% increase.
Also, assuming you dont have 200 dex, but in case you do, the dex effect for success % stops after 200. So 201 and 2000 would be the same.
Rain and party members also give you bonus, if your party has high ranked for w/e skill ur doing, you'll get more bonuses. E.g. If you're weaving, a rank 6 weaver will give u more bonus compared to a rank C weaver.
IGN: SOSAsurius
Style: Pure Archer