I think the food at Chilis tastes exactly the same. We used to live near Canary Wharf and ate there quite often. Granted, I only had chips and salsa, Chicken Ranch Sandwich, and Chicken Crispers, because those were my favourite and I stuck to the same thing, but they tasted the same as back home to me. The only thing I didn't like was the price......but it was worth it when I was missing home.
I've never been to Texas Embassy, so I'm not sure about it as an alternative. I'm interested to hear what others say. I've always wanted to try it, but I've heard its a bit pricey. (I haven't actually checked for myself)