I wouldn't listen to your friends. They're probably telling you to go the Mac route because they want to justify their expenditure to themselves. Buy what you can afford or what you prefer. Mac owners can be pretty snobbish at times but the outcome is the same regardless of the machine used. I had a mid-2010 Macbook with slightly better specs than the one you mentioned and had to replace it because I found it just too slow to be able to handle Creative Cloud and other apps. The GPU inside was also pretty poor and couldn't even render WebGL 3D in browsers. This isn't a necessity for most people, but as a web designer, I need to be able to at least experience current web technologies. You'll also find it's sluggish without an SSD.
Personally, I much prefer the Mac OS to Windows 10 since it seems just a little bit faster and more intuitive in a lot of places, though you can get pretty much all industry software and some indie stuff on both platforms. I honestly never have any desire to urge people to buy a Mac/Macbook over a Windows PC or laptop. It's personal choice really, and plenty of agencies use Windows because they can build a suite of workstations that do specific tasks well for a fraction of the price for stock Apple products.
Whilst the build quality of Macs still feels very high, Apple are constantly removing features and 'innovating' in ways that actually annoys and infuriates a lot of people. If it was a toss-up between a Mac and a PC I'd build a PC that does exactly what I need, but I prefer Macbook to pre-built Windows laptops. If I had the funds though, I'd definitely opt for the
MS Surface Studio. This looks exactly like how I feel you should be designing on screen. Using your hands, not a mouse. When these come down in price I'll probably look to switch in a few years times, if they're still making them.
FYI, El Capitan is the OS version (I believe it's the current one). Apple tends to change up their naming conventions every so often. Previously it was wild cats (Snow Leopard, Mountain Lion, etc), now it seems to be national parks/geographical (Yosemite, El Capitan…). No idea who thought those up.