Well, assuming both have the 'light' modifier (Should be a safe assumption), since you can't dig faster than 1 block per frame, or 60 blocks per second, then the real difference is whether you're willing to sacrifice being able to wear your armor for the +2 (composite) reach. Since you're basically a god at that point in the game even with armor, it's not much of a contest.
I'm sorry. I should have been more clear. Basically, the maximum possible mining speed is one block per frame the game runs at. It runs at a maximum of 60 frames per second, meaning the maximum possible mining speed is 60 blocks per second. The 'light' modifier on either the picksaw or the gloves will reduce their tool speed from 6 and 4, respectively, to 5 and 3 (in other words, make them work faster). For the gloves, you can hit that maximum mining speed by getting a total mining speed bonus of 40%. For the picksaw, you need a mining speed bonus of 70%. In other words, for the gloves, you can get up to the maximum mining speed by using a mining potion (25%) and sun, moon, or celestial stone (15%). For the picksaw, you need a mining potion (25%), sun/moon/celestial stone (15%), and a mining outfit (30%) to achieve the same results. So, the question comes down to whether you want to wear your own armor, and suffer from a -1 effect to your reach, or wear the mining outfit, and have a +1 effect to your reach. Alternately, you could assume you're wearing a mining outfit regardless, which would mean the picksaw needs mining potions to be as fast as the gloves. Here's a TO post, if you want more info. http://www.terrariaonline.com/threads/mining-speed-and-you.159635/Wait what.
What does this post even MEAN?
I'm sorry. I should have been more clear. Basically, the maximum possible mining speed is one block per frame the game runs at. It runs at a maximum of 60 frames per second, meaning the maximum possible mining speed is 60 blocks per second. The 'light' modifier on either the picksaw or the gloves will reduce their tool speed from 6 and 4, respectively, to 5 and 3 (in other words, make them work faster). For the gloves, you can hit that maximum mining speed by getting a total mining speed bonus of 40%. For the picksaw, you need a mining speed bonus of 70%. In other words, for the gloves, you can get up to the maximum mining speed by using a mining potion (25%) and sun, moon, or celestial stone (15%). For the picksaw, you need a mining potion (25%), sun/moon/celestial stone (15%), and a mining outfit (30%) to achieve the same results. So, the question comes down to whether you want to wear your own armor, and suffer from a -1 effect to your reach, or wear the mining outfit, and have a +1 effect to your reach. Alternately, you could assume you're wearing a mining outfit regardless, which would mean the picksaw needs mining potions to be as fast as the gloves. Here's a TO post, if you want more info. http://www.terrariaonline.com/threads/mining-speed-and-you.159635/