Given the number of postings here that question the heat issue of external vs. internal sun shades, I feel the need to add a few more comments.
My primary issue was keeping the heat out ; privacy and ease of installation were secondary issues. I purchased my sun shades from Untitled Document
after first doing some homework on the subject. They were custom made on site ... a process that took less than 2 hours.
Why does your rig heat up when sun shines through your window? It does so because the sun rays strike your dash, chairs, and anything else inside and warm them up. If the sun rays strike your inside mount sun shade it warms that up too. Since that shade is inside your coach that warm shade radiates its warmth back into your coach... the heat can't get back outside the glass. My external shade blocks much of the sun's rays (94%) BEFORE they pass through the glass to heat up interior objects.
The Privacy factor is about the same with interior and exterior shades. Ease of installation must be much easier for interior, as is the ability to keep it clean, but after one year's use I have yet to have anything muss up my exterior shade other than an occasional bird doo doo. The high quality nylon material cleans easily with water... and soap if necessary. I've only had to spot clean once or twice.
That's about it for my additional comments. Hope that clarifies this issue of interior vs. exterior.