Which mode is more important, tablet or laptop? If tablet then the Yoga is the way to go. The Yoga is more a tablet with a keyboard than a laptop. The 4GB RAM is not upgradable, it is more than the 2GB minimum for Win 8 64 bit, and the harddrive is 128GB Flash, about 80GB usable. One of the Lenovo laptops we use at work is the X230 Tablet PC Win 7. You can get the non-twist version a little cheaper if tablet configuration is not an absolute. The next down version is the S230. Both are more laptop than tablet, you can get different processors and the RAM is upgradable. The X230 has more battery life and a better screen for using a stylus than the S230. I found the Lenovo S230 Twist Win 8 with an I7 processor, 8GB Ram, 24 GB Flash and 500GB harddrive for $869. Weight difference is 1/2 pound more and the battery life is not as good as the Yoga but it has a better processor and more memory. If you plan on video conferencing and storing lots of pictures it may be a better option.
Amazon.com: Lenovo ThinkPad Twist S230u 33476LU 13-Inch Convertible Laptop: Computers & Accessories
I would not hesitate to buy a Lenovo. I have a Lenovo laptop and 2 tablets at home. We have thousands of Lenovo PCs, Mini PCs and laptops at work and have very few problems. We also use Panasonic Toughbook C2s but they are $2500. Mine is an older version C1 with dual batteries. For traveling they are rugged but expensive.