I much prefer Win7 to Win8. More fine controls available to the user, less "smart" and "friendly" automation. Win7 does require a few updates - official and otherwise - to provide all the Win8-native functionality and compatibility I use.

Win8 does have a lot of new little features and improvements I like, even a few I find especially important. Some things I really like (fast file copies, fast startup/shutdown, etc) which don't actually matter much because they add up to mere seconds each day I operate my machinery. A few more things currently lacking in Win7 (like official support for DX12 and USB3.x) which aren't all that important to me now but might be essential a few years down the road. But overall it's just too little and too much of the wrong things, too bloated, too many tradeoffs. Even the new GUI arrangements I happen mislike are highly resistant to being retrograded without resorting to indelicate and ugly low-level hacks. Besides, I mostly use Windows just for gaming and find more and more of my (non-gaming) daily computing tasks can be done better, much better, on a linux. So, given the right software addons, the two versions are functionally almost identical for my current uses, I might as well focus on the one which offers better stability and less intrusive bloat.

Windows 7 is officially End-Of-Life anyhow. Microsoft will continue to provide critical security patches as necessary to address the most serious new vulnerabilities and exploits which turn up, for a few more years. But they will not work on any more Win7-specific content, apps, or support. Their development focus is on Windows 10, their support focus is on Windows 8 and server/enterprise systems. I kinda like the fact that Win7 is a "finished" product and Microsoft won't be actively mucking around with my core OS anymore, no more changes, no more add-ons, my configurations will stay where I put them and remain stable indefinitely ... but for most users the opposite position (having ready access to active software upgrades and support) is more compelling.

If you are planning to buy Windows then I'd recommend getting the current version, Win8.1. And buy yourself a real genuine bona-fide Microsoft OEM Windows CD/DVD, not just an online activation or user license key, so you can install and reinstall and migrate it all you like without any license-/key-related hassles. FYI, my experience with every Windows OS (desktop and enterprise versions, including recent Vista/7/8 versions) is that your install will suffer performance degradation and get sick after many months of activity - simple fact is that a clean nuke-and-pave install every 6-12 months is necessary to correct countless little ailments, and not having access to your own fixed copy of Windows wastes time and money or forces you to live with an aging Windows install which becomes increasingly less functional.

You currently have another option if you need a working Windows now but can't/don't want to spend money on it now. You can download the Windows 10 Beta (aka Windows Technical Preview) for free, and use it free until it expires (in a few months, I think). Read the beta terms carefully, you will only get a few weeks notice to migrate your data before the OS install deactivates. You will still have to purchase a Windows in a few months, but - who knows? - maybe you'll like Win10 a lot and just pay to activate the copy you're already running. And - again, who knows? - you have a timeframe of a few months for some sort of discounted student license option to appear.

Small caveat: while it is basically a fully stable and reliable (if slightly unpolished) new Windows, it is in the end an OS Beta and people using it are guinea pigs - so you cannot go far wrong with a backup strategy which preserves a copy of your valuable data on another platform (removable media, online storage, etc).