LED Driver, which do you prefer?

I am working on 2 designs at the same time, I may just produce a short run (say 10) of each of them just to play with, anyway...

Option 1 (good for 1 watt apps)
Voltage Boost
V boost range: 0.9-3.2V
Abs max limit: 6V
Constant Current 350ma (very flat even with 1.2Vin)
At low batt auto drop to 70ma
Up to 90% efficient
Dia: 0.60in

Option 2 (good for high power K2)
Voltage Boost (fixed out at 4.2V)
V range: 0.5V-4.2V (beyond will go DD)
Abs max limit: 5V
Current Output up to 2A <-- Good for K2
Up to 97% efficient (closer vin to 4.2V the higher efficiency)
Dia 0.60in


Option 1 is nice because it is constant current and auto adjusting forward voltage, where as option 2 is fixed at 4.2V output (will overdrive your LED)

Option 2 is nice because it can deliver up to 2 amps and also it allows you to basically use any battery you can find NiMh, Alkaline, Li-Ion, Li Primary, ect, and with a Li-Ion it is 97% efficient. Can be changed into quasi CC by adding resistor to the output (although lowers efficiency).

P.S.
Option 1 is already in design revision 5 and almost ready to go production, option 2 needs more work.

Just to give you all an idea of the complexity of one of these things here is revision 2 of the 6 Watt driver Dia = 0.80 in still needs to be made smaller!

Between the 2 choices, I'd pic option 1. Sounds like you're using an LTC3490 chip.

The more ideal option for me would be a buck/boost converter capable of 0.9V to 9V Vin. There's not many drivers out there with this range capability that I've been able to find (they're usually in the lower range with a lower max, or higher range with a higher min). I've looked into making my own circuit, but ultimately, I have no way of getting the boards mfr'd at a reasonable cost, so I gave up efforts in the design.

Good luck. If you can shrink the board of Option 1 to be small enough to fit into a AAA light, that will make it very flexible and I already have a light I'd like to use that in.