From what you've said, it sounds like flexibility is valuable to you. A cashback card or a transferable/cashable point-based card would probably be most valuable to you, based on that.
I'm sure you'll get a lot of answers, but you might want to look into the Chase Ink business card, depending how the merchants you buy from for your business (especially the server hosting) are classified. The Chase Ink Bold/Plus earns 5x points per $1 "on the first $50,000 spent annually at office supply stores and on cellular phone, landline, internet and cable TV services." If you can find the merchant code/classification for the $4K web server hosting charge, you can determine if Chase would classify it as a 5x category and, if so, that's a no-brainer. Otherwise, many would probably either recommend the Chase Sapphire Preferred, or the AMEX Fidelity 2% cashback card. Assuming you'd be using the card in France, the AMEX card might not be for you, as there are foreign transaction fees on that card.
Chase UR points earned by the Ink/CSP can be redeemed for cash at 1 cent per point, travel at 1.25 cents per point, or transferred to many different partners (airline, hotel, amtrak), if you want to play the mileage game a bit.