There are a few factors to consider when choosing an LED strip:

Voltage

LED strips come in a few different voltages, with the most common being 5V and 12V. I'm going to use a 12V strip as the LED output will be brighter despite using only a short strip of LEDs.

This is the LED strip I used for this guide. I chose it because it stays cool and has LEDs packed closely together, resulting in brighter LED output.

Type and brightness

You might notice there are different types of LED strips (SMD 3528, SMD 5050, etc.) The difference here is the physical size of the LEDs on the strip.

If you're interested, this is how the SMG measurement translates to LED size:

Type LED size SMG 3528 3.5x2.8mm SMG 5050 5.0x5.0mm

LED density

Another big factor is LED density -- the number of LEDs per meter is a common measure.

Heat

Make sure your LED strip doesn't get hot enough to melt the strip holder, which you're probably printing in PLA -- some super high output LED strips can do this. No need to go overboard.

LED color/temperature

Color temperature refers to how "warm", or "yellow" the light is. You probably want a colder, whiter light for your 3D printer.

I went with a cool color temperature of 6000-6500K.