Best shifting system for inexperienced rider?
 

I am an avid cyclist but my girlfriend is not. I built her a bike last year on a Shogun mixte frame, and made it a single speed according to her request. We went for a few rides and it was all well and good, but she's decided she would like some gears. Right now, I'm either considering doing like a 1x7 set up with a rear derailer or a 3-speed internal gear hub set up. Right now I'm sort of leaning towards a 3 spreed, but I'd appreciate some extra insight. We're mainly going to be doing leisurely 5 to 10 mile circuits on trails.

Coming from a 30-speed derailleur drivetrain, three-speeds can be miserable. Coming from a single speed bike, three-speeds are useful and wonderful little mechanisms.

One nice thing about Sturmey-Archer three speeds is the large number of factory shifters they offer: two kinds of twist shifters, two kinds of trigger shifters, a thumb shifter, a bar end shifter, a downtube shifter, a 'stick shift' shifter and a dual paddle shifter.

I knew from the start that my wife would not take well to re-railing a chain over front and rear gear clusters. I guess to some people that seems like madness and chaos. Plus she would never consider looking down at the gears to resolve any questions on gearing or clicking noises, etc So I went with an 8 speed Shimano IGH and she likes it. Plus you can shift any time; moving or standing still.

The internally geared hub sounds like a good choice. More than 3 speeds might help to future-proof it in the event that she decides 3 isn't enough at some point.

Internal hub is the easiest. Yoy can shift while the bike is not moving, you can have a chain guard, and they don't get out of adj.

If you go vintage 3 speed you want to use a larger cog. They were originally geared so the middle gear was for flats and then a gear for downhill and uphill the uphill gear really wasn't low enough. If you replace the back cog you get a gear for flats and 2 for going uphills. You end up coasting down hill. I think on a newer bike the chain ring is going to be smaller making this modification less necessary.

Sounds excellent. I would love one but can be hard to find one in the trash pile, I generally run a 6 speed derailleur in the back...a bit complicated but the wide gear spread and cheap price make it fun...non-indexed systems do make noise if not shifted right. No front gear changing is very nice.

My wife has a 1 speed bike I am really looking to putting a 3 speed hub on...glad others are in my spot as well.

If you go with the 1x7, she will be used to the sound and feel of the shift if she wants to continue, and get a new bike with more gears. You can also change the freewheel\cassette if she wants a closer or wider range of gearing.
You are correct sticking with a single cog up front, theying to learn to shift both when you are starting with a multi gear bike can be a noisy, frustrating challenge.
And some people, such as my wife, the "Queen of Cross Chaining" never really get it.

You know, this isn't rocket surgery. Anybody can learn to shift--my kids could both do it when they were five or six.
I like the idea of an IGH because they're simple and bulletproof, but even if she winds up with a triple, just put it on the middle ring and tell her to shift the other one. She'll figure it out. Don't encourage women to be incompetent--society does enough of that.

Grip Shift.

My trail-a-bike has a factory installed grip shift so clearly you're not alone here. I think trigger shifters are much easier, but in controlling how many gears are shifted and just shifting.

That's what I've done with my kids. Start with just the RD then work up to both.
Easiest to hardest in my experience with the kids:
Bar-ends/thumbies
triggers
gripshifters- more a hand strength issue with kids
downtube (although they all wind up using downtube shifters on their road bikes (they're all from the 70's)

No experience with brifters so I can't comment.

yeesh ... girlfriends ... good luck. here's a word of advice though, don't cater to her too much now, cuz it will just get worse

My wife is not a fan of derailleur gears but does not mind the 16 speed (2 by 8) indexed system on her townie... am sure that if I built up an IGH wheel and installed that the smoochies would never end. :)

She had purchased a new Electra mixte with a 20 speed indexed system and really loved that... the issue with the bike was that it could not be racked on the bus so we returned it and she likes her vintage Peugeot even more.

I have a bike with an 8 speed internal geared hubs and it shifts very easily when stopped or moving, it has to be the easiest way to shift. However, downside is they add a lot of weight, three speeds are probably lighter, but if your has a lot of hills the 7 or 8 speeds will come in handy. My bike came with a Shimano and it wore out after 6 years (rainy and winter riding). Replaced with Sturmey Archer. If you go this route be careful with gear selection. When I switched hubs I also needed to switch chain rings to compensate.

Good luck!