Heal vs Barrier
- Heal can save a teammate. Barrier can't
- Health gained from Heal sticks around and can be used after damage is taken. Barrier health does not and can thus be totally wasted or waited out.
- Heal gives a small short speed boost. Barrier does not.
- Barrier gives more health temporarily than Heal and is not affected by GW.
- Barrier has 180 s CD. Heal has 240 s CD.
Overall, I personally feel the advantages tilt more towards Heal for me.
Heal vs Ignite
This is pretty much an offensive vs defensive issue. The other point to consider is how reliably you will be in Ignite range when you want to use it. Artillery champs tend not to be, so it can be tricky to apply it. To be fair, it's not to hard to end up in range, but you can easily end up just out of range and not get Ignite off.
I personally play Ziggs a lot and when I play someone closer range, usually Veigar, I still feel I can use Heal more reliably.
Heal vs Cleanse
Cleanse is very limited in its use cases but is very useful in those cases. I personally never end up taking it because I'm not used to it and would rather stick with Heal and just try to dodge the CC instead.
Heal vs Teleport
Not all champions have good plays they can make with Teleport. An extra person showing up from across the map or the ability to return to lane sooner is always nice, but making good Teleport plays is harder than it seems, especially in non-coordinated teams. Because of the level of coordination, Teleport is significantly better in pro play than it is for the rest of us.