Luckily, the stats answer this for you.
Renault are the least balanced - and by quite some way - because 100% of the constructor points would have come from Vitaly Petrov. This is due to the fact that Petrov never finished ahead of his team mate when both cars finished - it may be reliability of machine, reliability of driver, favouritism within the team or a season-long fluke. Whatever the reason, it tells us that, in 2010, Kubica was by far the better driver and Renault would have lost a position in the championship by relying on their rabbit instead of ensuring a balanced team. A similar situation occurred in 2008 with Toro Rosso - Vettel would have scored no constructor points. They addressed this by having Vettel was poached by a higher team, and that higher team now has their first world championship in each department...
Ferrari are unbalanced too - Massa scoring three times as many constructor points by this method than Alonso. As if the radio transmissions didn't tell everyone that Massa was a number 2 driver, the stats do (and they do with Barrichello in 2009 too). However, Ferrari's speed and reliability (and Brawn's in 2009) give them a strong position - by commonly finishing both cars, they get very many points indeed. This is further exemplified by Toyota in 2009 and BMW in 2008, both of whom get promoted to second place overall by virtue of so many double-finishes above their rivals (BMW score three first second drivers and five second second drivers in 2008 - with 16 points finishes from 18!).
Edit: Now I have the numbers (different computer), I'll post the teams in order of most to least balanced/reliable (and pace - the cars' actual results. There ought to be a better way of evaluating pace, but I'll stick with this for now) and the places they would have gained or lost my way.
2010
Balance: STR (+2), Williams (+1), HRT (+1), Force India (-2), Red Bull (0), Lotus (-1), Virgin (0), McLaren (-1), Sauber (0), Ferrari (+1), Mercedes (0), Renault (-1)
Reliability: Ferrari (+1), Red Bull (0), Mercedes (0), Williams (+1), McLaren (-1), Renault (-1), STR (+2), HRT (+1), Sauber (0), Force India (-2), Lotus (-1), Virgin (0)
Pace: Red Bull (0), Ferrari (+1), McLaren (-1), Mercedes (0), Renault (-1), Williams (+1), Force India (-2), Sauber (0), STR (+2), Lotus (-1), HRT (+1), Virgin (0)
Taken in isolation, you have each factor being tempered by each other - teams at the top of each field improve unless they're near the bottom of another, and teams at the bottom of each field fall unless they're near the top of another. Comparing teams more directly, you have a faster and more reliable Ferrari beating a more balanced McLaren (instead of the reality), a more reliable and better balanced HRT beating a faster Lotus (instead of the reality), a better balanced and more reliable STR beating a faster Force India (instead of the reality). I can spot a mild anomaly in there (Force India/Sauber) but looking at the numbers it's all due to Force India's catastrophic record of bringing both cars home - a truly dreadful record in one field can destroy your season. As well it should.
2009
Balance: Toyota (+2), Red Bull (0), Sauber (+1), Force India (0), Brawn (0), Ferrari (0), Williams (0), Toro Rosso (0), McLaren (-3), Renault (0)
Reliability: Brawn (0), Toyota (+2), Ferrari (0), Renault (0), Sauber (+1), Williams (0), Red Bull (0), Force India (0), McLaren (-3), Toro Rosso (0)
Pace: Brawn (0), Red Bull (0), McLaren (-3), Ferrari (0), Toyota (+2), Sauber (+1), Williams (0), Renault (0), Force India (0), Toro Rosso (0)
As above - McLaren's dreadful balance and reliability may not have hindered Hamilton's late season drivers' title charge, but it certainly dropped them behind other manufacturers. Pace when it works is no good for titles. Little change elsewhere - but the midfield gets a spread of just seven points at the end of the season, compared to 35.5...
2008
Balance: Williams (+3), Honda (0), Toyota (+1), McLaren (+1), Sauber (+1), Renault (-3), Ferrari (-2), Red Bull (+1), Force India (0), STR (-2), Super Aguri (0)
Reliability: Sauber (+1), McLaren (+1), Williams (+3), Toyota (+1), Red Bull (+1), Ferrari (-2), Honda (0), STR (-2), Renault (-3), Honda (0), Super Aguri (0)*, Force India (0)
Pace: Ferrari (-2), McLaren (+1), Sauber (+1), Renault (-3), Toyota (+1), STR (-2), Red Bull (+1), Williams (+3), Honda (0), Force India (0), Super Aguri (0)
And again. Ferrari's below-average balance and reliability hurts their championship - where they have pace over McLaren and Sauber, both teams are more reliable and better balanced and overtake them. The same can be said for Renault - Piquet's literal makeweight status destroys their speed-alone-based 4th and drops them to the bottom of midfield. Honda's awful season is unchanged despite their great balance, because they have neither pace nor reliability. The top two are covered by 2pt (compared to 21), with McLaren clinching the title at the last race despite going into it with a 1pt deficit to Sauber. Toyota nip a place from Williams by a point - going into the race 4pt down. RBR and Renault go in a point apart and come out a point apart, both failing to score. STR just nip a place from Honda by a point having gone in dead even.
And then there's the back of the grid. Can you seriously tell me that the Lotus is the better team because seven people fell off the road in front of one in a single race of a 19-race season than Hispania, who brought their cars home together 50% more often (or, discounting classified non-finishes, 100% more often)? I reckon it was the faster car of the two, but what use is speed if you can't drag it round 190 miles more than five times from nineteen?
"To finish first, first you must finish".
And if everyone builds a car that finishes, you still need to be faster!
Yes and, for the ninth time, this doesn't affect the drivers' championship. In order for the teams to win the teams' championship, they need to make sure it's the right hardware for both drivers and be reliable and be fast. It's not the right hardware if it's only given to one man and it's not a team sport if you only have one player. It's the team aspect that this fixes - it doesn't touch the drivers' championship.