Those are tough staves to decide what to do with.
There's a reason why the heart is off to one side like that. The side with the thinner rings was under tension and the thick side was under compression. If you split it the first way the thin side will draw into a bunch of reflex. If it was a bigger log, the thick side would be straight or deflexed, but since they are both small, there's a good chance that both halves will draw a reflex. If you split it the second way, I'm afraid it'll want to pull a sideways bend on you.
If it was mine and the bark ran straight with no twist...I'd saw it right down the middle of the stave...not the heart. I'd do it like the first pic... just in the center. That way you have plenty of wood in both halves. Leave the bark and sapwood on it for a while and seal the belly, especially on the little one. Now all this is just my opinion, so don't take it for fact.
Some pics of how the bark runs would help.
Most of them I cut that small, split with a bunch of prop twist and end up as fire wood
I hope these turn out better for you.