Which one do you want honestly? I have all 3 and they are great
Shield portable is exactly what it is, portable, imagine it like a portable xbox 360. Only problem is out dated, with the 2013 release, and having the Tegra 4, it would be nice if this was updated to Tegra X1 and resold.
Shield tablet K1is probably what people had wanted the first time the shield portable was released more updated than the portable it has Tegra K1 which is better than tegra 4. It has a 5MP camera (Or higher i think) Takes pics at 2K (Is higher than 1920X1080) Dunno the exact stats, records 1080P video at 30 fps, can screen cap for recording videos, of games you play, or stream direct to twitch services. you may wanna invest in a shield controller to help with that though.
Shield TV has the best money. Two options at 16GB for $200 or 500GB for $300 you basically have a console that outclasses PS3 and Xbox 360. Able to play PC games like a boss as if you actually had one, it has the almighty Tegra X1 and built in ethernet or wifi, bluetooth, 3.0 usb support, micro sdXC support and also built in chromecast as well. So you can use any other device with chromecast support on it. (Example your PC with chrome web browser) and you can also do mirrorcast which basically uses chrome cast like wii u tablet. 2 screen projection. You may have to sideload some apps as the one in the built in google play store are very limited to what it can find there, but as long as you install exfile explorer, no problem with app importing.
mx player also recommended for good playback due to hardware encoding for all 3 devices, as stated by the site offically recommended. Really good. ALL have 4K support. dualband connection for 5GHZ AC and 2.4GHZ B/G/N
One thing to note, the portable is less supported now and days, having up to 5.1 marshmellow, while the tablet and shield has lolipop 6.0, each device will receive updates individually, meaning just cause one got updated they all will not, is all time based. Expect apps that haven't been updated to work with newer versions to not work until fixed.
If you have any other questions you can ask me