Well, I really like both, and in general, I've grown to think they are equally fantastic. I'd seriously not be surprised one bit if they have a few of the same people working in the kitchens because of specific characteristics of a few dishes, especially the tandoori chicken. IMO, 7sp tandoori chicken seems to always have a more pasty spice coating, and is never really charred, whereas Rivaj's is usually nicely charred, pretty damn spicy, and less spice paste coated. I HAVE, however, on two counts, experienced tandoori chicken at Rivaj that was a dead ringer for what I always seems to get at 7sp. It might seem totally coincidental, sure, but for as many times as I've been to each, the heat levels, uniqueness of dishes, the chutney offerings, and that tandoori chicken similarity - I just wouldn't be surprised at ALL if there were a few ppl that work at both restaurants.
In general from my visits:
Rivaj's food tends to have more heat across the board, and their tandoori chicken is better - more of a dry spice, and well charred bird parts. (but again, note, that I've had a pastier, wetter, version here on a few visits.)
Unique offerings - the edge might go to 7sp in general, but in the past few months, the edge is VERY slight. Rivaj's buffet has grown by 4-6 dishes, AND they definitely have broadened those few dishes.
I definitely REALLY like both. A few months ago, I would have said 7sp is better, but today? I'd say it's a toss up which might surprise everyone who likes 7sp, but has not been to Rivaj. IMO, since the offerings are different at both places each day, you'd have to make multiple visits to gather your own findings. In general, however, across multiple visits, Rivaj tends to have more heat, and better tandoori chicken. When either are ON, they are definitely ON, though. I'm usually QUITE happy to visit either.
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