Isle of Skye vs Glencoe Itinerary

I would do the Glencoe option. The Skye option will involve a full day of travel to get to Kyle by train and then renting a car. I live near by Dunvegan and wouldn’t want to contemplate that journey by public transport with so little time actually in Skye.

On the Glencoe option I would rent a car at Edinburgh airport. Drive to Glencoe via Callendar and then return the car at the same location and fly to London.

The Skye plan makes me nervous in case of train problems, and/or a flight cancellation. I'm just a bit more open to that plan than Jacqui but would say to take the morning bus from Kyle to Inverness as a more robust plan. However it all feels rushed, and risky.
Maybe the afternoon train then Cal Sleeper Inverness to London?
The Glencoe plan wastes too much time going to and fro Fort William for the car.
I would say to rent from Arnold Clarke at South Street, Glasgow. Taxi to and from the depot and Queen Street station, Glasgow.
I expect to hear next week about a new regular bus service from Edinburgh to Fort William which I assume will route through Glencoe.
You could also gain most of a day and take the Caledonian Sleeper from Glasgow or Fort William to London, or a late flight from GLA. If the latter rent from AC at their off airport site in Paisley.

With limited time, Glencoe sounds your best option.It’s only 3 hrs from Edinburgh or 2 from Glasgow if you hire from there.I’d hire from either city and enjoy what is mostly a wonderful scenic drive with many hiking options on route once you hit the Highlands.

What level of ‘hiking’ are you geared up for/experienced with? That will allow some suggestions to make the most of your time and see as much variety as possible.

The advantage of Skye is having some outstanding hiking, often quite low level but which is truly spectacular and of course, you have the sea and cliff top hike options etc.

Glencoe is truly spectacular also.

Walkhighlands is the go to resource online for walkers/hikers and covers the whole of Scotland.

Thanks for the tips everyone. I am definitely leaning toward the Glencoe itinerary given it would require significantly less travel. I don't mind that on the front end as much, but I'm going to want to get back to London asap the morning of our last day so my bf can see the city a tiny bit. Skye looks so amazing and I'll be bummed not to see it, but I also want to keep this as chill and relaxing as possible.

Re hiking: It does seem like the advantage of Skye is that the hiking is less difficult but still with a ton of payoff. Back home in California I am quite capable of doing hikes that are rated moderate to difficult on AllTrails -- I am down for strenuous in terms of fitness -- but less confident with anything super technical. (My bf is a rock climber though and more capable and confident than me, so it'll help to have him with me.) I've been scouring Walkhighlands and there seems like there will be plenty I can handle in the area — Lost Valley and Pap of Glencoe appear to be in my scope of capabilities, maybe Buachaille Etive Beag too.

And yeah, it sounds like it wouldn't be the best idea to try to rent the car in Fort William. Mostly the train ride seemed really nice and would minimize the amount of driving my bf would have to do, but would also be a waste of money if we're going to be renting a car that day anyway. The appeal of driving from Glasgow is that it would be easier to make a Loch Lomond stop and I hear the drive is more scenic in general than what we would do coming from Edinburgh. But again, seems silly to be buying train tickets for any amount on top of the daily car rental fee. What would be a nice stop to make on the route from Edinburgh up to Glencoe?

Really my ideal trip would have been to do WHW but we don't have time.

I'm afraid I'm like a broken record. People who know me will predict that if driving from Edinburgh I suggest going via Stirling and the Trossachs in preference to Loch Lomond.
The mid way stop being Callander.

Here's a different idea that might interest you, especially if this is your first trip to Scotland and you are likely to visit Scotland again in the future. The first time we visited Scotland, we sampled a couple of places . This helped us to decide which areas to visit on several subsequent longer visits to Scotland.

Nights 1 and 2, Edinburgh.
Night 3 Glencoe

Nights 4 and 5 Skye
Night 6 Glencoe again - check out Kingshouse Hotel for this night since it is close to the south end of Glencoe
Day 7 return car at Glasgow airport

The stops are all about 100 miles, 2:15 apart. Days would be split between a scenic drive and a 3-4 hour hike. Picnics save time. Using the Skye bridge would be quicker than the ferry.