There are as many flavors of independent chapel as there are priests.
That's the problem -- there's no consistency. Some tread the fine line between keeping the faith, and avoiding extremism. But all too many get into apocalyptic movements, unapproved private revelations, infighting, you name it. There are too many personalities involved. There's usually someone who "owns" the Church, which complicates matters further, since he/she/they will have an undue influence over the whole liturgical life there, including the priest himself.
I grew up in an Independent chapel, and I have been to several others since then. They are very much "hit and miss" but mostly "miss".
They can be good for "keeping the Faith" and respecting the Mass, but they lack the professionalism that the SSPX brings to the picture. It's nice to have their stability -- it's the next best thing if you can't have an end to the Crisis :)
Granted, it's a sloppy 2nd, but 2nd place none the less.
God bless,
Matthew