There are a number of issues that can cause a slow boot sequence, the brand of mobo plays a small part in how quickly a system POST's and boots into the OS. WHen it comes to the POST and boot sequence, it has more to do with the BIOS settings and associated hardware than what brand. This is not to say that some brands do not POST and boot faster than others, but to say that there are BIOS tweaks you can make to speed up the POST and boot sequence.
For example, the boot order can slow down the sequence or a system with a dedicated hardware RAID controller card that houses the OS drives will boot slower. Having legacy devices enabled that the system is not using (like serial ports, infrared ports, parallel ports) will also slow down the sequence.
Before swapping mobo's, I would suggest tweaking the BIOS for optimum POST and boot performance.