Just depends on what you want to do. Both are good careers and both will keep you employed for a very long time. C/C++ and lower level projects has been growing some again given the IoT land today. So you aren't limited to only wireless, scientific or financial markets if you are a C/C++ person anymore. Same time, being a good web dev is a solid career and can be a lot of fun. I have done them both, I started in C/C++ a really long time ago and it has always served me well, but I also have done a ton of work in ASP.NET, node.js and a bunch of other web tech.
Personally, you've been doing the C/C++ for awhile, so if you are interested in web this might be a super interesting and fun challenge for you. If nothing else you will learn what you like more. Frankly, demand being what it is, many times you can make more money as a web engineer writing javascript or python etc than you can as a low level C++ engineer.