The Toshiba may be the lightest and thinnest of these Ultrabooks, but it also has the most built in features. It has a full-sized HDMI port, VGA, three USB ports (including USB 3.0), Gigabit Ethernet, separate headphone and microphone ports and an SD card slot.
The ASUS has two USB ports (one being USB 3.0), a micro-HDMI port, a single audio port and an SD card slot. It comes with adapters for Ethernet and VGA. The Acer has the fewest ports; you only get two USB ports (no USB 3.0) and full-sized HDMI, as well as an audio port and an SD card slot.
The Toshiba Satellite Z830 (PT22LA-001001) Ultrabook costs $1399, as does the Acer Aspire S3-951, which has a similar configuration (Intel Core i5-2467m CPU and 4GB of RAM) but it comes with a 320GB hard drives instead of a 128GB solid state drive like the Toshiba. The ASUS Zenbook UX31 (CUX31E-RY010V) Ultrabook is the most expensive at $1999. It has an Intel Core i7-2677M CPU, 4GB of RAM and a 256GB solid state drive.