I agree that the flash rate may be different, but it will be adequate; an exact load match is not necessary. You just need enough load to prevent a "hyperflash" (BCM error) or "no flash" situation. In fact, every car model out there has a slightly different flash rate, so.... However, the solid state flasher is obviously a much better solution, as it would be unaffected by the number of LED and/or incandescent bulbs in the circuit and whether you are trailering or not.
BTW, LED bulbs have multiple LEDs oriented at various angles; combined with reflector housings, viewing angle is not typically an issue either.