The big downside for me at Junior's is that Junior's Taco shop does not make it's own hard shelled tortillas, instead it uses pre-baked hard shell tortillas. This really detracts from the overall flavor of many of the hard shelled taco dishes. Prices are competitive and the service is fast, however seating is limited and in my opinion you would get a lot more bang for your buck at a Roberto's or Fresh MXN.
Prices here are competitive and the daily special's offer really good deals. I frequent Jose's often and can't recall having any bad meals. The pollo asada, carnitas, and shredded chicken are all very lean and high quality. Service is usually quick. One of my favorite Taco Shops in San Diego.
Super Sergio's is a tweener, hovering between a 3 and 4 star Taco Shop. The reason I crossed over and gave it 4 stars instead of 3 is because (i) it's the best option in the particular proximity of Kearny Mesa/Clairemont/Convoy street, and (ii) I really only go hear late at night on the way home from wherever after I've had a few beers (e.g. I've just left O'Brien's and I'm not in a condition to drive). The reason Super Sergio's would normally edge down towards 3 stars would be that Super Sergio's doesn't really offer anything that stands out or any remarkable specials.