I can't comment from experience on either of your options, nor have I read much about them. There's a review of the Canon
here. In short, it seems to be acceptable optically, but poorly made and low on features. With regard the Tamron, TBH it seems hard to believe a lens for that money wouldn't show every bit of its budget price.
The tele lenses that get recommended here (and elsewhere) most often are the Sigma 70-300 APO and the Canon 55-250 IS, both of which are some way above the price of your current considerations.
HTH