Both are trace mixes. TMG is Tropica Master Grow - but has lately been renamed to Tropica Plant Nutrition or something like that. I understand its the same as TMG. Don't know what CSM stands for.
TMG is a pre-mixed liquid fertilizor whereas CSM is in the powder form. Many folks use TMG while many use CSM. Seems to me that both have worked well as well as Flourish. I believe Tom prefers TMG over CSM but don't know the reasoning.
I found a link on the APC which has a comparison of the makeup of each fert. The table was put together by Giancarlo Podio. Fertilizer Comparison
The ratios are difference, the chelator is also different and better suited for our tank's KH in TMG.
I'll address this more later when I start delivery of the Barr's matrix micronutrients(BMM). Probably mid-late summer. It's 5x more than CMS but 20X cheaper than Flourish or TMG and better than all of them.
I'm not worried about TMG or SC F being a competitor, unless they drop their prices by 5-10X, which they will not, the BMM will do better in the market due to far lower shipping cost and better ratios specific for aquatic plants, as well as better more specific chelators for our purposes.