I think your question was fine as is.
What you're telling us is you're choosing between two types of laptops, and you want to know if LR will benefit more from one of these types than the other.
In Lightroom is depends on how you set it up, and your work flow.
IF you're using the drive as an only drive, for your libraries, database, cache, image files, etc.. then you will certainly experience the overall difference a FAST SSD can make if properly configured, and for some tasks even more of a difference, while for other tasks no difference at all.
If you were using this drive only for your OS/Programs and you were plugging in additional drives, then depending on how these are configured and the tasks divided, you 'might' not notice much difference.
I mention a FAST SSD because some which are included with laptops are fairly slow and the impact felt. If you keep in mind that an average laptop hard disk transfers data at 50-70mbps, and a fast SSD can exceed 500mbps (not all laptops, but any supporting SATAIII can) you can see there's a difference. But the real speed difference isn't in the raw data transfer speeds, it's in the 4k speeds.
Try this: Google AS SSD, it's a SSD benchmarking utility. Basically, it processes a certain amount of files, and then tells you raw transfer speeds, 4k speeds, IOPS, etc. It transfers the same amount of files if testing an SSD or a regular hard disk. Using this program to run a benchmark on an average laptop can take well in excess of an hour, often several hours. Try it. With a fast SSD on my Lenovo x201s
it completes the test in roughly 15-18 seconds. Obviously there is a huge difference in the time it takes to move data around.
How YOU personally will feel this difference depends on what tasks in LR use file transfer (some of them), or what tasks could benefit from a fast cache (virtually all of them).
And of course you'll see significantly reduced boot times, faster times to load programs, and better performance from any program using the SSD as a scratch or cache disk. Most describe an SSD as changing the total character of their laptop, or feeling the difference normally felt when upgrading to a next generation machine. So.. going to a next generation machine AND using a fast SSD.. big big difference for you.
About ultrabooks. I think for most people these make a lot of sense. They're a great value and offer really good performance. But as you've noticed they are limited, and this is when a higher spec laptop in a 'near' size/weight category can make a big difference.. both in price and performance. My x201s with the cost of adding a fast SSD costs nearly double what an ultrabook costs. It's been worth every penny.