Edit: Removed inappropriate quote. Sorry bout that.
It's nearly impossible to balance many monster PCs throughout their
entire progression as a character. It is a case of 'rate of growth.' ECL characters usually start weaker, but have a "faster" rate of growth due to often powerful racial features which cannot be duplicated by any level of PC.
This is kind of hard to explain and will likely become a gross oversimplification (due to the sheer number of variables involved in true balance of a game this complex), but if you think of character progression in terms of two lines plotted on a graph, x-axis being Character Level/ECL, and y-axis representing 'Character Power,' you might imagine that the slope of the lines would illustrate their 'power progression'. It would vary slightly by class, but we'll assume typical PCs progress at an even rate (read: slope 1) from the origin (we'll use the coordinate level 1, power 1 as the origin) all the way out to (level 20, power 20). Moving horizontally (to the right) along the x-axis from (1,1), PCs with an LA and racial HD don't enter the graph until slightly before their respective ECL. For this example, let's use an ECL 4 character, which we'll estimate to start around coordinates (ECL 4, power 1.5), as it is well established that a character with 1 class level and several LA is typically far inferior at that first level. At that point (ECL 4), standard PCs are well above a monster PC in terms of relative power. In order to catch up, the monster race's slope (read: power progression) will (or at least should) always be greater than that of a Standard PC's. Just how much greater will vary depending on the specific monster (and his ECL; the greater the LA, the greater the slope). A heigtened slope can be explained by powerful racial features that are not available to (and cannot be duplicated by) standard PCs, as monster features become oh so much more effective in conjunction with the HP, saves and abilities that class levels bring.
Properly balanced, I would GUESS that most LA/ECL characters might intersect the 'Standard PC level vs power' line at (or more than) halfway from whatever their starting ECL was to ECL 20. ((20 - starting ECL)/2) <= Standard PC.
Balancing is a tricky issue, and there are likely all manner of monsters (with misassigned LA/HD) that defy any rules that emulate the general pattern.
Regardless, do not be surprised if a Level Adjusted PC who seemed underpowered at first, grows to catch and often surpass the normal PC in power. Similarly, characters who seem initially balanced with regular PCs may pull away from the group. Of course, this all depends on the features of the race and how well they work in combination with the monster's class levels.
Well, maybe i made some sense to someone with all that rambling.
Or maybe I'm just as confused as the next guy.
