As far as battery performance goes, it depends on the individual device. Some tablets have large batteries and great life, some smartphones have small batteries and short life. But most smartphones have longer standby times than most tablets. Actual use times vary all over the place. Choose a few of each that would suit your needs, then check the battery life. And remember, having wifi on eats batteries a lot faster than having it off. The same for 3G/4G, GPS and Bluetooth. The same phone can last one person 6 hours a charge and another person 3 days a charge. Choose mainly by how you're going to use it. Do you want it to be pocket size? Do you need a large screen? Do you need a telephone? My personal choice is a phablet - a phone with a very large (for a phone) screen - like the Samsung Note.
Tablet has don't have more features that comparing to smartphones. Smartphones has more advanced features and it can do more operation as computer.
If you are looking for a cheap but good quality tablet, I would recommend uPlay C70. It's running the latest Google Android 4.0 ICS, has a powerful ARM based 1.2GHz CPU with GPU, capacitive multi-touch screen, front-facing camera, expandable memory, and HDMI port to output video and game to your big screen TV. http://www.uplaytablet.com/uplay-android-4-0-tablet-pc-7-inch-capacitive-screen-512mb-ddr3-ram-arm-cortex-a9-1-2ghz-cpu-1-3mp-front-camera-1080p-hd-4gb-139-99-special-pre-order-price-79-99/
today i'm still use smart phone (android) for daily communication. and i'm use laptop and pc for my work. .