I wonder why Tor Browser, Tails or Whonix are the most preferred ways of browsing Tor. What's wrong with manually doing a transparent proxy and routing all traffic over Tor through iptables? Why do it is a bad idea? Assuming, manually routing all traffic through Tor is done by a person who's familiar with Linux, networking, etc. then is doing it still a bad idea?
first the easiest one, because of error-proneness:
i'm pretty sure the configuration (and code) of the mentioned projects is reviewed much more often than the configuration of someones single setup.
and its not just about how accessing the network, it is also about the clients and their configuration:
--> the idea is to be not just anonymous (by hiding the IP), but also not traceable/pseudonymous (by vanishing in the masses of homogenous users)...
hence blocking some IPs more or less than the usual Tor user, one not so wide spread addon installed and/or a pretty special resolution of your browser window and you are pretty easily trackable.
e.g. hardening the browser is a huge task! and also the devs of the mentioned projects are also working hard to make the fingerprint of their users look even.