These are both jpgs. So... 24bit?
If with 8bit vs. 16bit you mean the art style associated with the computer systems of the time (i.e NES vs. SNES) I'd say they are more 8bit.
16 bit to me would mean higher resolution and more colors.
Those images have way too many colors (11 colors each) to be practical on any 8-bit console, and the colors used are not appropriate to an 8-bit console's color gambit.
They do, in fact, very roughly approximate the "low-fi" style of 16-bit console games like Earthbound on the SNES, which include certain hallmarks of 8-bit-style art, like hyper-saturated colors and pure black outlines, but within the greater color depth afforded by a 16-bit console. However, the overall level of detail is low, even for an 8-bit sprite, the proportions are wonky even for super-deformed style, and they don't read particularly well.
In other words, technically both sprites require 16-bit console hardware, but the aesthetics of both are sorely lacking (the first one more so), which is what's making people say they look 8-bit.
They look more 8bit to me, as mentioned above they are pretty small resolution. Most sprites on SNES were at the least 32x32, though tiles were often seen smaller, when you could find the tile borders I mean, as the quality went up exponentially at that point.
I'd also say you are really wasting pixels there. I'm not really much of a pixel artist myself, but I see too much black in them. I think you could use those precious pixels for more detail, letting color contrast mark the borders between sections instead of wasting a whole black line. Final Fantasy 3/6 sprites are great examples of this.
On the SNES at least, RPGs used 16x16 character sprites for a good chunk of the console's life, until around late-1993 to 1994 when they mostly moved up to sprites typically being 16x24, going as large as 32x32 if the character's size warranted it - though the most notable RPG franchise on Sega consoles, Phantasy Star, used 16x32 sprites from the beginning. The sprites shown here, for comparison, are 19x24.
And from a pixel art perspective, the overuse of black is probably the least of these sprites' issues, though the second is less obviously flawed.
EDIT: Wow, 3 more posts in the time it took me to write this out >.<