I vote for plasma, I did it with my grinder and cut off wheel and it worked well. The Plasma would be the fastest and probably the cleanest. Less grinding afterwards.
What are you replacing them with? MORE has a good deal on some tabs, 1/4" thick!
As stated earlier, if you have access to a plasma cutter, use that and then clean it up with a grinder. I did mine with a 4 1/2" grinder. It was a bit of a pain, but not too bad.
Crunch