I would agree if I used my phone as my "primary browser". Your "primary browser" is your goto device for consuming books, news, email, social media, videos. But for me, that's my iPad. I don't use my iPhone at home really at all. I use my iPad at home constantly as my primary browser. And when I'm mobile, I don't really do any "primary browsing". When I'm mobile, my iPhone serves as a communication and "lookup device". If I need to look something up, my normal sized iPhone is fine.
And if I do go mobile and I expect to want a primary browser, I pack my iPad in a little messenger bag and bring it with me. But that's not usually what I need when I'm out.
So if your iPad is your primary browser, you just want your phone to be as slim and portable as possible.
But yes, if I wasn't all-in on the iPad, and I could only have an iPhone, I'd probably agree and go with the + model.