Prayer also depends on -- how much time is devoted for prayer.
For example: One hour of prayer by one person = One minute of prayer done by 60 people.
Disclaimer: Below is my opinion, what I have learned and experienced about prayer
1) Repeat 1 mala (108 times) mantra (e.g. Ohm) is only needed IF I can't manage to do "1 proper Ohm" at once
2) Many people do group praying, but when it's just multi-loudspeakers it won't work; it must be my 'heart-felt' prayer
3) IF I am desperate and cry out in
NEED, prayer works best (But Surrender is a tough one for me, as I like to stay in control)
4) IF I pray to God for Help, but all the while suggesting God what to do, it doesn't work; I don't do that when going to my surgeon !!!
5) When the ride is easy, I easily forget to pray, hence no experience "how to pray". Better to practise and start early, drive slowly to reach safely
I see God's Grace as a kind of Love-affair. Usually girls are not interested if a guy is boring, not showing interest, demanding etc.etc. (or they must be very desperate). My relationship with God is similar. The more effort I put in my relationship, the more I get out of it. Seems logical & fair too.
*) Many more, but these 5 come to mind now