OK this is my 2cents on manual batts vs auto batts!! 
I have a 510 and a 901. My 510 came with my a manual batt. My 901, which I have had way before my 510 came with an automatic batt. I really like what I have seen from my 510 manual batts in terms of vapor prod. and throat punch. At first I thought it was due primarily to the manual battery, but, recently I have acquired a manual batt for my 901. This has totally changed my opinion. Now, I do not think it is the battery that is providing the vapor prod. and throat punch, I think it is due to the ATOMIZER. The 510 atty is just far superior to the 901 atty. I have NOT noticed ANY improvement in VP or TH with a 901 manual battery.
Here is my take:
Manual Battery
Pros- no accidental firings due to environmental factors(however they can get stuck)
, better control of vapor, ability to preheat atty(good for burning of excess juice in moderation)
Cons- Inconvenience of pressing button, Accidental pressings of button ie. burn hole in pocket or body parts)
Automatic Battery
Pros- Ease of use(no buttons)
Cons- Accidental environmental misfirings(sound, battery sticking on and damaging atty
BOTTOM LINE: The ATTY is what makes the DIFFERENCE!! IMHO
I have a 510 and a 901. My 510 came with my a manual batt. My 901, which I have had way before my 510 came with an automatic batt. I really like what I have seen from my 510 manual batts in terms of vapor prod. and throat punch. At first I thought it was due primarily to the manual battery, but, recently I have acquired a manual batt for my 901. This has totally changed my opinion. Now, I do not think it is the battery that is providing the vapor prod. and throat punch, I think it is due to the ATOMIZER. The 510 atty is just far superior to the 901 atty. I have NOT noticed ANY improvement in VP or TH with a 901 manual battery.
Here is my take:
Manual Battery
Pros- no accidental firings due to environmental factors(however they can get stuck)

Cons- Inconvenience of pressing button, Accidental pressings of button ie. burn hole in pocket or body parts)

Automatic Battery
Pros- Ease of use(no buttons)
Cons- Accidental environmental misfirings(sound, battery sticking on and damaging atty

BOTTOM LINE: The ATTY is what makes the DIFFERENCE!! IMHO