Well I went to my local mech lab and checked it out myself. Sure enough, with max armor, and engine the Jenner has 11 tons free, while the Cicada only has 10. But then I thought: What about with smaller engines? Well since I have school work to avoid doing I made a chart!
I assumed that both mechs would use endo-steel structure and nearly maximum ferro-fibrous armor (232/238 on the Jenner, 268/274 on the Cicada). I also only went down to ~100 kph, because neither mech should be going that slow. I plotted free tonnage versus top speed (with speed tweak) because those are really the relevant stats here, and when two engines had the same weight I only used the larger one.
You can see that, due to a quirk of engine weights, there's this sharp drop with the Cicada at around 130 kph. Slower than that and the Cicada is up on the Jenner by 2 or more tons. They're even for a bit, then the Jenner is clearly better. Another thing to keep in mind here is that you can free up a full ton on some Cicadas (the 3A, 3C, and 3M), without severe risk to your weapons, by stripping armor from the arms.
So what does this mean for our beloved bug? It means that you should invest in a 300 XL engine, and learn to live at the snail's pace of 133.7 kph. You won't be winning any speed competitions, but you will bring a lot of extra punch to the fight. You can still hold your own against a light mech (but you should never engage one-on-one in any mech unless you have to). The 300 XL leaves you 15 tons to play with; the Jenner would need to drop it's speed to 119.6 to get that much space. This is the true advantage of a Cicada (in my humble opinion).
EDIT: This is not to say that builds with bigger engines are bad. I run several with 325 XL and the 330 XL from the X-5, but I encourage everyone to play around with the 300 XL.
TL;DR VERSION
The 300 XL is the most efficient engine for the Cicada. You run at 133.7, and have 15 tons for weapons and equipment with max armor. No other mech in the game can match that combo of speed and firepower.
Edited by Darwins Dog, 11 August 2013 - 07:53 AM.