Generally, episiotomies are only done for Fetal distress and forceps deliveries. You won't even necessarily have one with a ventouse/kiwi, it depends how well your perineum is stretching. There is something called buttonholing where it also might be done, where the perineum gets holes in and can lead to a very nasty tear so an episiotomy is preferable. But that's rather unusual.
As others have said, it's not really an either/or choice as if you need an episiotomy the head will be far down in the birth canal, making a c-section very difficult to do. That said, if they were thinking about taking you for a 'trial' of forceps in theatre, where they're not completely confident they can deliver the baby with forceps, you could request to go straight to c-section instead. But it depends on where the baby's head is, position etc. as to how easy it will be to do a c-section as doctors do try to avoid doing them at full dilatation.
In terms of difficulty of stitching together, an episiotomy is considered on a par with a second degree tear. Most heal very well, I've seen a few recently where after a couple of days you could barely tell it had been done. That doesn't mean some don't get infected and sore, of course they do, but it's not guaranteed to be a disaster. My sister had both an episiotomy AND a c-section at the same time (failed trial of forceps) and she said her episiotomy didn't cause her any problems at all and healed very quickly, barely any pain but her c-section scar caused her a lot of pain. I know this is anecdotal but it's just to show that it's not a fait accompli that an episiotomy will cause you agony.
I always feel a bit sad when I see no episiotomies unless absolutely necessary on birth plans. I absolutely understand the reasoning behind it but It makes me wonder if they view us as scissor happy maniacs - I promise we're not! I've known midwives who've been qualified 2 years plus who've never done one. I saw once a labour where the head crowning was very slow - they suggested doing an episiotomy but as the baby was okay she refused so they didn't. They will listen to you.
As for avoiding one, there's not much you can do to avoid emergencies but the best way is to try and avoid having an instrumental birth. The best way is by being mobile in labour, possibly not having an epidural as it does tend to prolong the pushing stage of labour, thereby increasing your risk of having forceps etc. But equally if you're having a long labour and you're tired you won't be able to push well if you're knackered so you have to weigh these things up as you go along. But pushing in different positions rather than being semi-recumbent so being on all fours, laying on your side etc. can all help.
Try not to worry too much about it. Easier said than done I know but discuss it with your midwife antenatally and if there's time in labour, get the doctors to discuss why they might want to do one and the pros and cons of having one vs. having a c-section.