I think IFT is a great way to gain experience, you see sick people granted they may not be acute but their still sick, use them to your advantage.
You can learn something from every patient you see, well almost everyone
It's true that you can learn a lot about different medical conditions and pt presentations in IFT. The thing is, unless you're doing challenging critical care work, IFT present little challenge or opportunity to develop critical thinking skills. In most cases, the pt already has a diagnosis, you're told what drips to run, what type of O2 admin, etc. Unless you're a CCEMT-P, you're not titrating drips on standing orders in most places. If the pt decompensates in some fashion, most places require you to contact OLMC for anything past the ABC's and your ACLS algorithms. How's that challenging?
911 offers the opportunity to come to your own conclusions regarding the pt presentation and decide on a treatment plan without having someone else already figure that out for you. You don't typically (except for maybe a pickup at the MD office) have the benefit of labs, CT, MRI, ABG, etc. to guide your Dx and treatment decisions. You have to figure it out for yourself.
Honestly, the best answer is to do both. I was lucky in that for my first job, seven months in IFT, I mainly drove a CCMedic. I ;earned a lot right away. Then, I worked for a hospital that did both 911 and IFT, depending on the shift.
I've noticed that strictly 911 medics largely do not fully understand the long term repercussions of their treatments. They don't fully understand what happens to the pt after being dropped off. The strictly IFT medic may lack the critical thinking skills to accurately Dx and treat pts in the field when starting from scratch (no chart, dx, etc.), so to speak. They'll also be inexperienced in handling all the dynamic conditions that the streets present. MVA's, a pt crashing on the top of a five floor walkup with no help, an arrest in a tight apartment with furniture and clutter, violent pts, risk/reward of stay and play vs load and go when around the corner from a hospital, how to move an intubated pt through that tight apartment and down the stairs w/o losing the tube, doing field CPAP (I've yet to see an IFT bus carry it), why it's a bad idea to start it in the house if no easy egress, etc.