In l'électeur's answer here, he claims (with such confidence that he bolds the belief) that the correct way to say the English sentence
"If I had turned right back then, I wonder what would have happened."
It seems like the reason for his statement is that instead of the plain ~ば, it should instead be ~ていれば (and that なった should be なっていた).
Furthermore, according to 新完全マスター, for 反実仮想 either ～ば or ～ていれば is acceptable. Yet, they only give examples of the latter, indicating that the latter form is preferred.
Note that in this case, the second clause is plain past tense.
My questions are then:
- Why is it preferred to use ~ていれば for counterfactual conditionals instead of the plain ~ば?
- Should we use the ~ている for both the if clause and the then clause or does the then clause not matter?
- Is there a difference in meaning between the two grammatical forms or is it just a clarity of writing thing?
Note: I realize that this isn't limited to ~ば and seems to apply to ~たら and ～なら as well, but for the sake of an easier title I chose to talk specifically about ~ば vs ~ていれば.