The quality of a restaurant varies over time, as cooks come and go and ingridents/flavor may change. For example. Shinsengumi's (Fountain Valley) tonkatsu soup base is still very good, but the noodle's quality has gone down a bit. Also the guy w/glasses isn't cooking ramen there these days, he was my favorite chef there. Foo Foo Tei's quality went down over the past couple of years after the owners decided to take it easy and visit the kitchen less.
Mentatsu used to be known for its chahan (fried rice), rice dishes, and gyoza, but not the quality of their ramen. But recently their gyoza's quality has declined. They also have a new/young Mexican chef cooking noodles this year, he's not very experienced but he cares -- I sit at the bar and watch him taste-test (chew-test?) the noodle before he'd serve it, and if he thinks it's over-done, he'll dump it in the trash and start over. If you go to Daikokuya in Little Tokyo, the Mexican chefs there cook with timers -- like microwaved "ding ding" food.
In colder months, the more spicy & oily ramen served at places like Kohryu in Costa Mesa might hit the spot better than a lighter soup. It's said that the oil on top of the soup can help retain the heat better, but makes it less healthy to consume on regular basis. The hardest ramen soup base to prep is probably vegetarian, because you're missing the oil from the 4 main components (soup base, ramen, topping, oil).
