Enlighten me about the differences of IGBT and MOSFET please

Hello guys, Can anybody explain the differences of IGBTs and MOSFETs? Yesterday I found an article entitled What is the Difference Between MOSFET and IGBT (http://www.apogeeweb.net/article/66.html), which theoretically explained this question to a certain degree, but still i want to ask you guys about the same question in another way, such as application prospect of the products. Could you please enlighten me about something related to this? I have a couple of relating questions. As far as i know, IGBTs and MOSFETs are very similar devices, and operate (superficially) in pretty much the same way. MOSFETs are better at higher frequency, but because they're not quite so good with high currents we generally need more to equal an IGBT, so can be more expensive to implement. I see a lot of the newer Chinese tig welders are using IGBTs now. But also some still keep MOSFETs in their newer model welders. Is that because IGBTs are cheaper? IGBT is basically an electronic switch used for high efficiency switching. They were known to be more reliable than mosfet technology, although I have heard that some manufacturers have still returned to updated improved mosfet technology. Maybe that is because IGBTs require more complicated control circuitry than MOSFETs, with photocoupler, etc. And this makes manufacturers choose MOSFETs . Any thought? I guess one of the biggest problems with Mosfet based machines may be not the chip, but how its seated on the heat sink. Many fixing screws are too tight, preventing the chip from moving, under thermal load. I would say the first TIG set I bought the screws were very tight by the way. As top manufacturers started using IGBTs and advertising this, implying it's significantly better (I'm not saying it's not better, I have no idea) so Chinese manufacturers followed, making people think "ooh, it uses IGBTs, just like Miller, I'll get that". So What do you think? The Igbts which are known to be the most reliable are the German Siemens Infinions. Some of the cheap Igbts however have a failure rate higher than mosfets. MOSFETs may need to be changed as a set too and it can be a pricey business for likes of EWM. Contrary to popular belief, manufacturers don't choose to change a thing 'because better', it's cost based, which You can not deny, always has been and always will be. The only time that changes is if it could seriously damage a reputation, and then only if they care about such things. Designed properly, either will make a good welding supply. Right? Thanks for your time.

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