For now, since I'm not actually participating in the sporting end of boxing, I think I'll keep practicing the techniques and strategies, but stick with my karate gloves, or practice with nothing.
My reasoning:
Pro "Light hands": While practicing with heavy gloves, your body mechanics to generate speed and power will be slightly different. For me, I'll use my shoulders more, for one thing that I know of, probably other subtle changes as well.
One of the things I know I have to work on (a lot) is not telegraphing my movement, and moving as efficiently as possible. So, If I practice with "light hands" I'll be training my body how best to move in that configuration, which is how I will be using it. One of my biggest "tells" that I'm throwing anything is that my shoulders start to lead, or my head leads slightly (not enough to present a target, but enough to give my attack away.)
Meanwhile, I still practice the basic attack combinations, and the "never say die" mentality that is so crucial to boxing, and so often overlooked in karate.
Pros for "heavy hands": I do know how effective it is to practice with heavier gloves, then when you take them off, you feel like you're weightless. Compared to the gloves, now you're lightening fast. Your muscles are better able to handle the endurance, and blasts of power, and you're mentally toughened to go longer.
Conclusion: For me, at this stage in my training, I think I will continue with little/no weight. I already have some of the fastest jabs/hands in my dojo, and I credit that to a lot of work on the speed bag, and double-ended bag. (The light ones that will come around and hit you in the face if your guard drops. Lotsa fun!) I can also generate a good amount of power in my hits, and I don't want to train my hands to be dependent on padding, but to know my own limits.
If I am going to be hitting faster, I want it to be because I am throwing technically correct punches, not punches using stronger muscles. At this point, I'm not connected with a boxing coach who can help me do both.
But, I do credit a lot of my most useful fighting skills to my start in both boxing, and as a pint-sized football lineman.
I think boxing is severely under-rated these days.