Babar vs Rahul?
Let's be honest, what have both achieved at the moment across all formats? Babar has had more opportunities, and when you look at the white-ball stats, you see a player who is really playing well. You look at the rankings, and he's second in ODI and in the top 5 in T20I. So what you see is a player who is really doing well, but he isn't having world-class performances. In test matches, he is still uncertain, and perhaps that is because he doesn't have the patience to continue overnight, or it might be because of a white-ball mindset in test matches.
KL Rahul, someone with presumably a lot of talent, has done well in his international career as well. He is a utility player as he keeps wickets and bats well down the order. His white ball stats are also quite good, but are they world class? No, they aren't. He also is at a good position in the batting rankings. In tests, he is also not a reliable batting option, as seen from his batting stats.
So Babar is undoubtedly the best batsman in the Pakistan National Team, whereas Rahul is far behind the likes of Kohli and Rohit, who are in a league of their own.
Babar's batting average in ODI cricket is quite high, and he has shown performances in the format. He bats at 3, and strikes at about 87.
KL Rahul's batting position changes quite frequently. He is sometimes asked to open, sometimes pushed deep in the middle order, and sometimes doesn't even feature at all. However, he does well to make performances when it matters.
As far as shot selection goes, KL Rahul has more shots to offer, and he has power. For someone with the ability to smack a cricket ball, it is criminal that he doesn't continue punishing oppositions after a flyer of a start. This trend was seen in the IPL, where he'd get to his 50 or 40, and then the scoring rate would drop and drop until it reached a SR of 130 and he'd get out. KL Rahul has the type of shot selection which allows him to hit sixes when he connects the ball nicely.
On the other hand, someone like Babar relies more on placement and timing the ball along the ground. His off-side game is excellent, as he has a variety of shots, but his leg side game could be improved. Apart from the flick, front-foot pull, and on-drive, I haven't seen him target the leg side at all. A right hander should easily be able to punish players who bowl on the leg side, and Babar needs to develop leg-side shots. He relies on getting his runs with minimum risk, but nowadays, risks need to be taken for more reward.
In the end, it comes down to the type of player you like to watch. Personally, Babar is more orthodox in his batting approach which is why I like watching him, but that does not downplay the class of KL Rahul.
Both can improve (Babar on the leg-side, KL perhaps on his temperament and shots straight down the ground.).
Both are good players, and can become better, and that's all I think there is to it.