The Apple Smart Keyboards for both the 10.5" and 11" are great. They actually have a very decent typing feel, mainly because of their decent 18 mm key spacing. And the fact they don't have to deal with Bluetooth is great.
In any case, the other problem with the 11" is that it too has only 4 GB RAM. To me it seems the 4 GB matches the performance of the 10.5" well. The performance of the 11" is more future proofed, but the RAM is not there to match it, and this year there are several applications that are coming out that will likely be able to make use of both that extra performance and that extra RAM.
I currently have the 64 GB 10.5" Pro. I'll probably buy an 11" with 128-256 GB storage sometime after it gets 6 GB minimum RAM. I have no need to get a 1 TB iPad to get that 6 GB RAM.
For LTE, I just tether to my iPhone. It seems our usage patterns are very different.