Many things get confused in this forum, leaving readers even more confused then before.
First of all - the 2.4 Ghz systems have flaws - but far less then the 72 Mhz systems. If they use less power depends on the individual systems you compare. A new 2.4 computer system with all the options may use more power then a simple 72 Mhz Tx. WIth the high capacity batteries we have today, this is not an issue.
Then we have people experiencing interference having problems with their gas engines. Yes, the ignition can still cause problems with the 2.4 receivers. The interference happens after the signal has been decoded. After the 'firewall ' and safeties the 2.4 systems use.
On this end the receiver communicates with it's servos still in the old fashioned way and is prone to interference.
To eliminate the problem, we had to go to a new designed receiver using a shielded data cable to send signals to the servos.
Few of us want to spend the money such a system would cost.
Conclusion - the 2.4 Ghz systems are the best and safest we can get. I have no doubt the rc industry will come up with something better and greater in the future. But until then my 2.4 radio will serve me well for many years to come.