I don't think it's a question of advantages as much as it is a question of your goals. YB Pastels and YB Spiders are great looking morphs and I guess you can plan to use them for other projects such as a YB Bumblebee or YB Super Pastels.

Your other option will give you ivories and they in turn will allow you to get 100% YBs in any pairings you do with other morphs.

So really it just depends on what you want in the long term to achieve your goals.