Palladium vs Nickle vs other catalyzer energy densities?

I've been reviewing some prototypes of LENR energy modules that various companies have mentioned that they would release. It seems to me that using Palladium instead of nickle produces higher energy output from the same size of the device. Take for example Deneum vs Rossi's E-cat or Universal Gravity which uses lithium and hydrogen. Per size comparison, you can get 15 kW from Universal Gravity's Lithium catalyzer, 25kW from the E-cat nickle catalyzer, and 250kW from Deneum's device.

My question is that isn't the most logical choice to go with the catalyzer with the highest energy density? And if so, why isn't everyone going for the highest energy density compound to use for their respective devices?

Quote from Alan Smith

There are a lot of factors rather than just energy output. Here are a few in no particular order..

Practicality of preparation and gas/electrolytic loading , ease of triggering, cost, toxicity, availability, durability in service, ease of containment (molten lithium for example is an escaper), thermal conductivity in bulk.

There may be m,ore.

Applying the all important KISS method of keeping it simple, which I've been assuming this whole time that you have been following, then isn't palladium the logical choice to use wrt. to energy and heat production?