Whether to follow the book or signposts in Hungary

I'm following the Euro-Velo Route 6 along the Danube at the moment and have been for around 1200km now. I'm using the Cycline Guides which are good but mostly supuflous when it comes following the actual path. Until I hit Hungary... a lot of the route is now unsigned and those that are in place don't inspire confidence. This morning they wanted me to go down a national highway - direct and flat I'll grant you but the book took on a beautiful, traffic free albeit slightly hilly route, as shown in the photo. Think I made the right choice even more so as two french cyclists I'd spoken to this morning came along as I've been writing this and described the road route, which they took, in very uncomplimentary terms!