To answer the question from the OP. Kits are the easy or lazy way to do it. I prefer to have more control of what the overall finished product looks like.
A customer of mine ordered a kit for his Fathom. To me the color bomb approach the kit takes really makes the game look like a$$, especially the backglass. I am still at a loss to understand how making the game all one color or a rainbow of color improves it in the least but to each their own. I am all for LEDs and their benefits when used to update the game to today's tech while leaving the beauty and ambience the designer intended. PinballBulbs warm white's are perfect for this.