Not certain about DataSift, but we used Gnip and part of the terms was you couldn't display tweets to your users directly off the firehose. I'd imagine DataSift has a similar restriction.
Besides that; neither give you access to private tweets or DMs, so you pretty much have to use the API for a client of any worth.
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I haven't really looked at it, but I don't think DataSift is intended for twitter clients to use.
Not certain about DataSift, but we used Gnip and part of the terms was you couldn't display tweets to your users directly off the firehose. I'd imagine DataSift has a similar restriction.
Besides that; neither give you access to private tweets or DMs, so you pretty much have to use the API for a client of any worth.