Greece or Switzerland in September?

September is probably one of the best months to visit Switzerland. It's one of the drier times of the year and the temperatures are mild. Go for it!

If the weather is your main concern, then as Tom said, Switzerland is beautiful in September. Also a consideration is the type of vacation experience you and your husband want to have. I'm assuming sightseeing is the main focus given the stated destinations. Interesting you mention Greece as it is very different to Switzerland both weather-wise and culturally. If you'd like a break from a busy travel schedule, then include a Greek Island...perhaps Santorini and its easily accessible by air from Continental Europe. Hope this helps... http://en.wikipedia.org/wiki/Santorini

I've always wanted to see Switzerland in the Fall with all of the vibrant colors of the leaves changing. It's such a beautiful country!

I think both would be wonderful in September, I love the Greek Islands, and Switzerland is beautiful also.. depends on what you want to do. The Islands would be a relaxing break from sightseeing ,, you could relax and enjoy the beach , but Switzerland is so amazing too,, and as noted if you wish to hike the trails would be snow free and drier then most of the year. I think you have chosen two completely opposite places, both good choices, so now its up to you to decide what you want to see and do. Good luck, what a lovely trip . I do also hope this trip is at least 15-20 days long as you have many places to see and alot of travelling inbetween, remember when you book two nights in a hotel that only gives you one full day at a destination.
( ps if you choose Greece look at flying from Rome)