Depending on which version/EHP/SP level you are on and going to, you can probably use SPAM to apply your support packages, but I would recommend you use SUM. Here are some of its advantages:
- Kernel: As somebody else already mentioned, SUM does everything, including kernel, sapjvm, igs, SPAM/SAINT update, etc., so you don't have to do those separately. It even unpacks everything for you.
- Time: While the overall run time is longer when using SUM vs SPAM, the time during which your users are affected, i.e. down time, is considerably shorter. It will probably only really matter for production, but the process should be "tested" in dev and qa first.
- Recoverability: Up until just before the down time, you can still back out of it without any restores being necessary. SUM prompts you to make backups before and after the down time, so recover time, if you do need to restore is much shorter as well.
- Future: I suspect there will be more and more cases where SPAM cannot be used, so you might as well start getting some experience with it. If you have done upgrades before, it will look very familiar; if not, you will gain some experience for future upgrades.