They are apples and oranges. One is sporty, other one is cruiser. Both are low on power but the Ninja manages highways much better than rebel. Tall people cannot ride a rebel but can ride a Ninja. Short ones can ride both. Ninja resale value is lot higher than rebel. I used to have a ninja and I sold it for more than I bought for.
Personally I think they are both too small. If you just plan to use it as a commuter bike that may be good but if you plan on really getting into riding and want to ride for fun as well as transportation why not get something bigger. I gurantee you will want to trade up about 2 weeks after buying one of these bikes and you'll lose money doing so.
I'd recommend starting out on a 500 or 600, both cruisers and sport bikes come in these sizes, the bike will also last you for a few years as opposed to a few weeks.
The Honda Rebel is way too small to take out on the freeway. It won't go 80mph! It would be OK around town only. The Ninja is quicker, but your better bet is to get a bigger bike, 400cc minimum, unless there are no interstate highways within 500 miles of your house!