Both Windows 7 & 10 are the best so you can use whichever you prefer.
But I would say Win 10 is better than Win 7 because of its significant updates and improvements but Win 10 has a very irritating problem which a updating Windows every week or so.
Win 7 is free from that and in this sense Win 7 is better from Win 10. So its up to you which one you will choose.
But I would not recommend Widows 8 or 8.1 they are the worst.