Temperature. If the bulb is not well designed to get the heat out, the elevated temperature reduces the life of the device. Bulbs with the same wattage that feel hotter are actually dissipating the heat better and should last longer.
Total energy out == total energy in. The energy in is electricity. The energy out is a combination of light and heat. More heat implies less light.
Also, a bulb with more surface area for coupling heat to the air will feel less hot than an otherwise identical bulb with less surface area. The larger surface area has less heat per unit area. Also, the LEDs in the hotter bulb may be above their optimal temperature range, so operating less efficiently, so producing more heat per unit of input energy.
So, for otherwise identical LED bulbs, cooler is better. ("otherwise identical" being a big caveat)
Of course, there is another factor: Not all light is suitable for our use. Ideal would be all light produced be in the visible range with whatever color balance the individual user prefers (I prefer "daylight white"). It is possible for a bulb to produce less heat, but mostly unusable light while another produces more heat but mostly usable light. So, while the overall efficiency of the latter bulb is lower, its effective efficiency is higher.
As usual, YMMV.