Both should have 10yr parts. The labor warranty you're speaking of is probably through the dealer only. You can opt for a 10yr, parts & labor warranty from either manufacturer. This should cover all of the components of the system, that are internal OEM components of the unit. External components or optional accessories would have to be specifically added to the extended warranty. I would strongly suggest the extended warranty. If you and the installing company happen to have a falling out, the extended warranty can be picked up by any dealer of the respective manufacturer, (might have a very small transfer fee).
The company I work for is a dealer for both, and both have their fair share of pro's and con's. I used to like Lennox more, but as of late I've been leaning toward Trane.
Keep in mind. If you have a compressor failure or coil failure on the 3rd-10th year, only having the dealer labor warranty, you will have to pay for refrigerant, 3-6hrs in labor (depending on the company), and any cleanup components needed. This could set you back over 1k.
If I were to choose a unit today to install in my parents house, it would probably be Trane. I like the way that they take care of most issues. Instead of putting a bandaid on it, they change the way they produce the product, (if there is a significant number of units that have the failures). Some may disagree with my choice, or statements, but this is what I see from my little part of the world.
I agree that the most important part of the process is the installation and maintenance. However, I also believe if you buy cheap builder's grade type manufacturer products, don't expect to get a Mercedes for Kia prices. There is a difference...
"The only true wisdom is in knowing you know nothing" Socrates