Ehhh, they're different skill levels but I wouldn't say one is more impressive then the other. Great wordplay and really well thought out internal rhyme schemes are equally as difficult. As someone who writes (And not to brag, I have come up with some pretty crazy metaphors), coming up with a simile or metaphor that's creative is really only a matter of being able to correlate subjects together with similar sounds words. It's dope as fukk, but not necessarily rocket science. Internal rhyme schemes, that are well thought out, not just "I'm super viscous, you too suspicion, your whole group is bytches, your Coupe is rented" type shyt, is fire as well. I'm talking really well put together internal rhymes, with multiple syllables, and it makes a full statement.
To me it's the difference between Jay and Nas. Jay was a master of wordplay but wasn't really big on flipping syllables (He could, but that wasn't what he focused on) because he's from the branch of Kane and Jaz O, while Nas was heavy into syllable usage because he's from the school of Rakim and G Rap. It's just takes a different mental capacity. I'm sure if you tried to sit down and write a well thought out metaphor and a well thought out internal rhyme, it would take the same amount of time.
I, personally, like rappers that are great at both. Like Loaded Lux. Most elite lyricist can do both.