I don't usually jump into topics like this, but I figure I'd toss my two cents in just the same.
I remember hearing that the SP artists tried to make Simba look like Mufasa. Mufasa is definitely more "filled out" than adult Simba is in TLK, but I don't think the SP artists quite managed to pull off the same look with SP Simba. There isn't as much attention to detail with the characters a lot of the time, and sometimes something as subtle as the addition of a few lines can spell the difference between muscular and pudgy.
Take a look at
this screenshot of SP Simba. The artists gave him the same slope-backed, large-shouldered appearance as Mufasa had, but they made his forelegs much too chunky (even his
thumb looks pudgy). Compare to
this screenshot of Mufasa in a similar pose.
I don't want to spend too much time on this topic, so I'll just post a few screenshots and let them (mostly) speak for themselves.
Mufasa's face (look at all those details in that mane)
SP Simba's face (His jaw is barely pronounced -- it's more of an extension of his cheek. And his mane looks almost like it's melting...)
And here's some full-body pictures of
Mufasa (it's small, but it was the best one I could find),
TLK Simba, and
SP Simba.