I prefer ceramic guides on the fly rods I build for myself. I like the way they feel when I cast.

Since so much of this depends on your own preferences, You may want try out both types of guides before you commit.

You mentioned that you have both kinds of guides available. After gluing the reel seat and grip, you can tape the guides on the blank and test cast it. Masking tape or electrical tape is sufficient. (I glue the tiptop on first as well.) Move the guides around until it casts perfectly. Take good notes on the final positions then take off the guides and start all over again with the other type of guides!

This is also a way to experiment with the number of guides. Some blanks seem to cast better with a different number (one more or less) of guides than recommended.

I am assuming you are doing this as a hobby. If you are trying to make money, this would take too much time!

If you experiment like this, you will probably discover what you like and may become as opinionated as the rest of us!