Not trying to tell you what to do unlike other posts.
The old model does the job it was designed for, it buys, rents and plays Tv, movies, music, photo slideshows, youtube (if that's your thing). Apple may have stopped manufacturing the device, but TV and HDTV still plays fine.
It's your choice, depending on your needs.
I used mine to allow me to view all my DVDs and BluRays (ripped into iTunes). I never need to physically scan my video collection again, looking for a film to watch that night, it's all at the touch of the Apple Remote (well, my old iPod Touch). I don't know how the caching will work on the new one, but the old one allowed me to store all my favourite movies on the 160GB hard disk, so the computer with iTunes could go to sleep.
Biggest benefit was I could load it up with movies, TV shows, photos, etc and take it with me on my (frequent) travels, especially with kids in tow. 7 hour stopover in Dubai, Singapore, Hong Kong, Kuala Lumpur, Sydney, wherever, no problem, plug it in, attach the HDMI to the hotel room plasma and I have 35 episodes of Bob The Builder or Chuggington to keep the little ones occupied while I repack and sleep. Four weeks away anywhere, I still have all my movies, photos, home movies, etc to show friends, relatives, etc.
My 2008 Mac Pro is nearly as old as my "obsolete" Apple TV,is it obsolete too ? So no more updates for my AppleTV ? Well I like it just the way it is thanks, after the train-wreck that was AppleTV OS v2.
Only you can decide, will you miss the internal storage ? Many would.
Or you could sell it on eBay, for more than you paid for it. We had £149 clearance price from Apple in the UK, they all went in hours. Now they go for more than that 2nd hand and no free postage.