Bulbs compared to lamp modules like the Cree CR6 and Sylvania RT6 are at a disadvantage as
1. The LEDs are not forward facing in A19 style bulbs, unlike the CR6 and RT6 modules, resulting in more light being trapped in the can.
2. The modules are engineered to dissipate heat from the LEDs within a recessed can housing.
3. If BR or PAR bulbs are used, the light spread is more constrained.
4. The CR6 has better dimming performance than the A19 and A21 Cree bulbs

I went with the kit because our rims were plastic and starting to break and crumble. It also gave a neater look in the ceiling -- no dark valleys or gaps. The LED bulbs generate so much less heat that dissipating heat wasn't on our radar, but I can tell you that after changing 6 cans in out family room -- with 10-14 foot vaulted ceilings, there was a noticeable lack of heat build up in the room.

I have both. The look of the kits is better, more streamlined and sleeker, but they both work just fine.

Kits look way better. Worth it. Heat drop is incredible vs. incandescents.