Interesting discussion. I think I'll go against the trend on this one.
I've spent years as an LTC in an airline renowned for its training department. Within the department the role of LTC is universally seen as the most demanding in the company but it is technically and monetarily a lower rung on the ladder.
Recently a lot of CPs have done the course to qualify as TREs and TRIs, many openly saying that they did it for the easier life. The TRIs in particular run recurrent and type rating training from a script and the TREs examine using the exact same criteria as the LTCs who conduct the majority of the line checks.
The difference is that the LTCs are providing the training while also running a commercial operation as PIC. And there is no script or position freeze on the line. We are also picking up errors from the SIM caused by a lack of quality and airmanship in the SIM trainers. Most of the LTCs have considerably more line hours than those in the SIM at the time they commence the role.
I appreciate that a good trainer, whether the SIM or on the line needs to be both motivated and also talented in the art of teaching, but in my airline, at least, the notion that the TRI is a more in depth or demanding role doesn't match my experiences or the feedback I hear from colleagues who've abandoned line flying for the SIM.
Recently a new CP in my airline became a TRI 6 months after gaining his command, which is not unusual. I can see that he will be good at that job, but as an LTC he'd be hopeless. Conversely attracting experienced CPs to become LTCs is very difficult.