So I can't decide between which of these nations is better. While I do want to go siamese to upgrade my war elephants and have a water based emblematic structure, I also want Persian LT of -25 industry cost. Will the Siamese LT make up for that? Note I have when industry during the entire game and wonder if the Persian LT mixed with the Egyptian LT would be a ridiculously huge boost. Would I get -50% or would I get like -33%?

Industry cost scales too steeply with number of territories and districts. A flat -25% discount on all industry cost (including cost of Shared Projects) will be more beneficial than already quite substantial amount of industry Siamese would bring. Besides, Caravanserai provides potentially more money than Floating Market of Siamese, depending on how large your cities are.

Yutterh wrote:
Note I have when industry during the entire game and wonder if the Persian LT mixed with the Egyptian LT would be a ridiculously huge boost. Would I get -50% or would I get like -33%?

Although I'm not 100% certain about it, percent reductions are applied to base cost value as far as I know. Therefore, total industry cost discount (on Districts only) after Egyptians (-10% on Districts) and Persians (-25% on all constructible) should be -35%.

One other point in favor of Persians is that your army will get extra movement for the turn when they start on the EQ. If you want to blitzkrieg, it's very useful.