It depends.
For most of what you do, a tablet would suffice. However, as mentioned above, typing on them is a bit of a bitch. I type quite a bit on my Droid X (basically a 4.3” tablet that happens to make phone calls) and I have to say that if it weren’t for the Swype™ keyboard that allows me to slide my finger, I would be driven nuts by the repeated impacts of pressing each “key” on a non-yielding surface.
There are some dual-purpose rigs out there that act as a tablet when you want and a netbook when you need a keyboard. The aforementioned Asus Transformer is but one. The Dell Inspiron Duo is another, and there are many more.
I had a first-gen 8.9” Acer Aspire One that I loved as I found it to be a great machine for my needs. I type a bit and even use command-key shortcuts (especially Ctrl-S, Ctrl-V, and Ctrl-C) so having a keyboard is a big plus on anything I plan to use even remotely like a computer. (I went with the Droid X as opposed to the Droid 2 because I do most of my computer stuff on a full-fledged laptop.)
If not for the sending of e-mail, I would say tablet in a heartbeat as they are designed for consumption of information (Youtube, ‘net-surfing…) and it’s only the typing thing that makes me think that a netbook may be better for you.
Also, you might consider a low-end laptop as some are comparably priced. My Toshiba T135 cost about the same as many netbooks but has beefier specs and a bigger screen, though it’s still quite portable; under 4 pounds and the same size as a 13” Macbook. (I use a Macbook carrying case for it, and it’s a perfect fit!) The T135 I have is now obsolete by two generations, but the comparable modern model (the L735) is twice as powerful as mine, comparably sized, and far better than any netbook or tablet. The MSRP is $608.99, but you might be able to find a better deal; I saved about $100 on my T135.