If you're looking to use a simple drop in like the Terralux or Malkoff the first thing you need to do is check the serial number on your light. If it starts with a "D" either is a simple drop in, if not they will most likely require a bit of work.
I have a 2D Mag using 6 Eneloops and the Terralux TLE-300M, 3D Mag using a 5 sub D battery pack (Mag Charger battery) and the Terralux Ministar31, 4D Mag with a Malkoff with a Mag Rebel deep reflector (both smo or op depending on my mood) and a 5D Mag with the older TLE-300.
A few thoughts/observations:
The Malkoff quality is exceptional, the heat sink is as good as you'll ever find in a drop in. It has great throw with good spill. Rated in otf lumens! The only down side for me is it's single mode. It's a very easy drop in if you use the original reflector. I wanted to try for the most throw hence the Rebel reflectors. To get the reflector to fit the head I had to cut the switch down. About an hour for an amature like me but I'm happy with the results.
The Ministar31 quality is very good but not at the level of the Malkoff in my opinion. I gave several of the TLE-300Ms to State Trooper friends of mine about two years ago and they're all still going strong.
I've heard people complain about heat management but I've used thermal paste when installing mine and had no problems. The reletively large Mag head gets toasty very quickly on high and I've noticed no dimming even after 30-40 minutes on high.
The beam on the Ministar31 is a huge spot with no spill. Not really a flood light as it will throw due to the volume of light but no spill to speak of.
I'm going to try to post a few pictures that may be helpful. Unfortunately, I don't have my Ministar31 light tonight. The lights will be the 4D with Malkoff (I believe rated at 260 lumens) and 5D with my oldest Terralux, the TLE-300. By the way, the Ministar31 is 3 mode.
Before I post further pictures I need to enter a disclaimer: I have not yet taken the time to learn to take proper pictures. I have a very nice Nikon DSLR but have not learned to use it beyond my daily needs. These pictures were taken with my 12 year old Sony Mavica. White balance, f/stop, exposure, might as well be Greek to me. Since I'm posting pictures for a fellow BLFer to compare drop ins I thought I could cover my inability with a camera by photographing a wall shot with both lights on but I was wrong. One of the drop ins came out looking like a wimp! A trickery of the camera, they are both very bright, so...
The Malkoff
Don't know why it has that green color in the picture, I would call it neutral to my eye, a very nice tint with great throw. This is the op reflector. The smo reflector is more focused but obviously not as good a wall hunter.
TLE-300
The Ministar31 does not have the funky star pattern, only the large spot of the TLE-300. The 31 is also a warmer tint and I don't remember seeing the tint-shift, darn, I wish I had it here! Oh yea, while the TLE-300 was rated at 600lm the 31 is rated at 1,000. I don't know about either of those numbers but I know it's brighter!
Hope this helps, and I hope this time when I hit "save" it works. The last time I tried to post on BLF I ended up with a massive post of blank space. Wish me luck!
(edit) Forgot the side by side,