While I cannot speak for the SES specifically, I've spent quite a bit of time in the SEL in the three different layups (paddled the Advantage, owned the Excel, and now own the Ultra), and I'm sure there's a degree of overlap.
IMO, the Excel layup is the way to go. The weight savings from the Advantage to the Excel is far greater than that of the Excel to the Ultra (full carbon). With the Excel, you have all the advantages named above: easier to load/unload, much faster to accelerate onto a run, etc. with very little difference in stability. Unless you're doing huge breaking surf, I wouldn't be at all concerned with durability (ie: 'playing it safe' with the heavier fg); the Excel layups are quite strong. I've also paddled their double, the SE2, in both layups-I wouldn't say the Advantage layup imparts much more stability than the Excel, but perhaps the difference is offset by the combined weight of both paddlers as compared to a single.
I do note that the Ultra boat is a bit more 'high strung' than the Excel version though. The roll rate is faster, and the boat does feel, as Watto said: 'corkier' (great descriptor, by the way). Most of the difference in feel, however, I attribute to the torsionally stiff carbon. There is little, if any, 'give' in the water-every nuance is communicated to you via the stiffer structure. This is wonderful most of the time, particularly when you're hammering hard through the messy bits, but if you're just cruising, it does require a bit more attention. I liken the carbon boat's personality to my Aprilia Tuono moto, if personification is permissible. It will putter around town or cruise down the boulevard, but it always seems impatient and mildly annoyed at being asked to do so. The Excel layup SEL has just the right amount of give (like the softer ruby shaft Epic paddle vs. the stiffer blue shaft version), and all the benefits of the greatly reduced mass, without communicating every little unnecessary detail of your conversation with the water.
As noted, if you can get to both SES boats, paddle each in some textured water, as there is the possibility that this model might be affected differently regarding the respective layups. Years back I owned several V10Ls in the heavier FG version. When I moved to the Ultra version of the same boat, I was initially quite surprised as in this make/model, the difference between the two layups felt like two different boats. There was no mid layup at the time; the difference in mass was far more pronounced, no doubt attributing to two vastly different personalities.
"Nice? It's the only thing," said the Water Rat, solemnly, as he leaned forward for his stroke. "Believe me, my young friend, there is nothing -- absolutely nothing -- half so much worth doing as simply messing about in boats."
'The Wind in the Willows'~Kenneth Grahame