I don't have a lot of experience with the i-gel and I've never used one in the field, but I've used them some in OR.
The different SGA's all have pros and cons in relation to each other. Traditional LMA's are usually very secure (not quite like an ETT of course, but closer than what I think most people give them credit for) when placed properly, but can take a fair amount of finagling to get seated "just right". And they do take a fair amount of practice to be able to consistently get a really good seat quickly. They are also affected more by an individual patient's anatomy than an ETT is, and probably more than a King or Combitube.
It seems like the i-gel is catching on in EMS (as opposed to other LMA's) because it is just so easy to place. Because it conforms to the patient's anatomy better than other SGA's, technique is less important and it doesn't have to be placed precisely. The downside is that they do seem a little less secure, but with a good tape job and some caution, that shouldn't matter too much.
As for intubating "thought it" with a bougie......yeah, you can do that with any SGA, some a littler easier than others. I suppose that skill has it's place and is worth practicing, but I think in most scenarios you are better off leaving the SGA in place as long as it is working. And if the reason you are switching to an ETT is because the LMA just isn't working well, than you should probably be pulling the LMA and intubating the regular way, because if the LMA is malpositioned, then it cannot be counted on to direct the bougie where it needs to go.
If you really want a device that you can place easily and then intubate though, the Air-Q is my favorite LMA of all time - not only is it really sturdy and easy to handle and place and has a built-in bite block, but it is also specifically designed for passage of an ETT. The Fastrach is an "intubating LMA" but it's really just an LMA Classic that is slightly modified to make passing an ETT a little easier.
A moderate amount of PEEP shouldn't be a problem as long as the LMA is seated well.