Scotland and Ireland, driving/ferry in 16 days? Are we Crazy?

"Justice" is a pretty broad term when it comes to traveling! So, could you see a "bit" of each in 13 days and feel that you have a sense of each country? Yes. Is that the best use of your time - that all depends upon your preferred style of travel and what your interests are. I get the sense from your post that your preference would be to spend the time going a bit more "in depth". If that's the case, you will need to choose one country and even at that, you won't see everything. One thing to keep in mind with both Ireland and Scotland is that once you get off the main highways, the roads typically are narrower and thus it will take you longer to get from Point A to Point B.

You don't give any details about your flights. A lot depends on the airports you can use as gateways.

It is not practical for me to fly anywhere but London, and then proceed to EDI (Edinburgh) or Dublin from there. N = night.

N1 - fly to London, sleep in London. This day is a 'buffer' day for arrival flight.
N2 - N7 fly to Dublin, a week in Ireland.
N8 - N14 fly to Edinburgh, 3 n Edinburgh, 4 n. car trip through Highlands, terminating at EDI (Edinburgh airport.)
N15, N16 fly to London, last full day in London (minimize stress to prepare for return flight this way.)

With only 14 days at your disposal you really should pick one country or the other - trying to visit both would result in not having enough time to do justice to either. I think most here will agree that two weeks is barely enough time to explore Ireland, particularly if you try to include time in the North.
Although non-stop flights are always preferred, a single stopover (especially if it's a short one) is really not that big a deal. I see several connections from Dallas to Dublin that are pretty convenient, especially the United flights via Chicago from where you can connect to Aer Lingus flights.
Taking the ferry from Scotland to Ireland isn't quite as straightforward as you may think. Many rental car companies won't let you take a vehicle from one island to the other (check the fine print) and even if they do you'll be looking at punishing one-way drop charges. Better to fly from Edinburgh to Belfast or Dublin and pick up another car there...if you must do it that way at all.
Renting a car in Ireland is a discussion all its own thanks to the vagaries of insurance coverage. Suggest using the forum's search feature to explore previous discussions on that topic and on the subject of driving in Ireland in general.

My husband and I drove around Scotland some years ago, on the search for "bleak and craggy." we drove along the east coast, Alnwick and Alnmouth, looked at Loch Ness , Dunkeld, Lockerbie, Fort William, Oban...did some whiskey tasting, so I vote that you choose SCOTLAND!

Thanks very much to you all. I apologize for not getting back to this thread sooner - it's been a crazy couple of weeks. Your input is very helpful.

Contrarian, I didn't give any flight info because that is something I'm struggling with - fly to Dublin and do Ireland first or fly to Scotland, first. Here's where I have currently found sanity, flight-wise: Direct flight from Dallas to London. Layover in London (about 4 hours) long enough to get through customs and to the gate for the flight to Dublin. Crash in Dublin that evening. There are no direct flights to either Dublin or Edinburgh from Dallas, so this flight, which helps me escape layovers in Chicago/NYC/Dulles/Newark makes the most sense. So that's how far I've gotten - at least a plan to get to Dublin through London, in a reasonable amt of time.

Here's the most pressing question: Is it possible/reasonable to rent a car in Dublin that I will use to visit sites in both Ireland and Northern Ireland, then take the car to Scotland on the car ferry out of Belfast to Scotland and use that same car to tour Scotland, & bring it back to Dublin to drop off at same location I rented it.

I think I read somewhere that you can't take rental cars from Ireland or Northern Ireland to Scotland, or the opposite direction - that rental car companies don't like you to do that. Does anyone know if this is true?

Any advice on car rentals in Ireland/Northern Ireland w/a trip to Scotland and back are welcome. And thank you all, again, for your kind comments to my post. -- HorseDoc

I don't know for a fact about taking a car between Republic of Ireland and Northern Ireland, and on ferry to/from Scotland, but like you I have seen others posting that this is not allowed, or carries a significant surcharge. Your best bet would be to ask the car rental companies directly.

BUT have you looked at the ferry routes? Unless you have a burning desire to see the southwestern coast of Scotland, south of Glasgow, you're going to be landing way out of your way.

Flights between Ireland & Scotland are frequent and inexpensive. Considering the precious vacation time saved, flying is by far the better choice if you are determined to visit both countries. As an example: from where we live, Aer Lingus is the best & cheapest airline, so we flew into Dublin and spent a couple of days there just to get a bit of a taste of Ireland, then flew to Glasgow & rented a car to drive around Scotland. Ended up in Edinburgh, flew back to the US via Shannon (only changing planes -- we didn't see Shannon or surroundings at all).