I can speak from experience on both sides of the fence on this one...
My SRT4 used a combo ( not in this order, all the time) 24.5psi of boost, race gas, pump gas, 100% meth injection, 100shot of nitrous. It was quiet a chemistry set...
I'm going to say the Ethanol has a higher output gain, as well as less chance for failure. Fact is... Meth injection parts are made of...... Parts. And parts fail sometimes. If your tuning the motor hard enough to see gains close to what E45 can offer, your really pushing the meth stuff hard and trusting it with a TON of your fuel needs. If an injector clogs, if a check valve sticks, if a line busts, fit a fitting breaks, if a motor fails, if a regulator by-passes, if a fuse pops, if a processes burns, if a wire tap loses connection, if a motor/ pump mounting bolt breaks, if a reservoir leaks, if a blend is off.... Any of those issues could, can, and do happen. And if your counting on alcoy injection to support your tune (more boost or more timing or adding fuel or all of those), and it does from 100% to 0% in the blink of an eye.. Its could be very very bad.
Besides availability, Eth only has two other draw backs... #1 on my list is that sticker on the pump that says, "at least 70% ethanol". Ok... 70% to 85% is a good difference. #2 pump wear. By running E30-E50, you've taken car of the pump wear issue. Razor is currently building a solution for us right now that will read the % of ethanol in the fuel line real time, so that pretty much also eliminates issue #1. Availability isn't going to change, and even still, I'd want E85 and/of a mix of it in my water/meth injection tank anyway, so they are even on that scale to me.
So if i had to pick one or the other, and not both.... I'd pick E45.
I used devilsown meth injection kit for years. They replaced 2 pumps for me, for free. They replaced 3 check valves for me, for free. The 4th check valve was a new improved version that was less likely to fail. I installed it while my motor was out of my srt4 getting a new short block, ported head, cams, and newest upgrade in super stock turbo tech. I was breaking the motor in, and had 400 miles on it, when I decided to run some windshield fluid through the pump to make sure the last batch of meth didn 't kill it ( again ). And to make sure the pump wiring engaged and worked like it did before. I put 2 quarts in the tank and drove to work on 6psi peak. Pump worked, controller worked, everything was good, so I stayed out of boost on my way to work and worked for 10 hours on Thanksgiving eve. As I left work at 2am, I started the car and it was "cammed" harder than it seemed like it had before... I figured, "well... Its cold, its got big cams, ported head, and 680cc injectors, that's gonna happen". I pulled out of the parking spot and the car slammed to a stop. I thought I just stalled the aggressive clutch. Hit the starter and it just clicked. I figured my battery was some how dead. Checked the battery with a volt meter. Got to thinking about it, and reached under the front bumper and pulled a charge pipe loose, and nearly 2 quarts of fluid poured onto my arm.... Tried to move the engine with a breaker bar , but it was seized. The check valve had failed for the zillionth time, and filled the huge intercooler up while I was working.
It bend every rod and twisted one so bad it hit the block and broke a piece off. A 400 mile, brand new engine, hydro locked.
That horror story being what it is... I would/will be using meth injection again. This time, I don't care what happens, I'll mount the injector higher than the tank. I also, like before, will only be using it as a knock deterrent, intake/valve cleaner, and charge air temp cooler. I will not rely on it for any forum of fuel or boost ( maybe a bit of timing via the ecu per the intake air temp ). If the system fails, worst that happens is that I got slower and I have to mail something off for warranty.
Ethanol is fairly fool proof. Ask a good tuner for a E40tune, and only run it with E 40 (or so) fuel.
I plan to run both. I loved see my charge temps cooler than abundant with 24.5psi from a tiny stock/modded srt4 turbo. And it had a big part in make 354whp and 407TQ on the stock intercooler.
