I am Billy Ssali (freelance local Tour guide in Uganda).
I would say that Rwanda has an added advantage over Uganda compared to the distance to be driven in the car, in Rwanda it takes 2 hours drive from Kanombe International Airport to get to Kinigi (Parc De National) while in Uganda it needs a minimum of 11 hours to drive from Entebbe International Airport to Bwindi impenetrable forest depending on which gorilla family you want to visit.
But Uganda has the large number of mountain gorillas so if your to consider that and the good medical facilities and good terrain, then you can give Uganda an thought.
Roads are not always good though.
Can't advise you to go to Congo since their security is unreliable, anything can happen at any time!
Not only that but even getting a Congo visa is not easy whether online or at any of their border checkpoint.
Roads are impassable, visa goes up to $135 single entry for Congo, Rwanda visa fee was reduced to $30 (but you need to apply online in advance).
Uganda visa fee is $50 single entry.
travel.stackexchange.com/users/798/BILLY SSALI
When I did my research a few years ago I read that the biggest likelihood of seeing gorillas is in Uganda, I haven't tried it myself though.
I was traveling around other parts of Uganda and it felt reasonably safe - we were using public transport and cheap accommodation.
It was a few years ago though, you should check the current situation (usually foreign ministries have travel advice service - e.g. from UK's foreign office ).
travel.stackexchange.com/users/44/Grzenio
Mountain Gorillas, which are said to be man's closest relatives are living in Bwindi Impenetrable Forest and Mgahinga National Park in Uganda, Parc Nationale Des Volcans in Rwanda and the Virunga National Park in Eastern DR Congo.
But Uganda has the biggest numbers and Rwanda is also good.
I advise you to visit: www.visitgorillas.com
wwww.aabtoursandtravel.com and get detailed itineraries for trekking these amazing creature.
Also call direct +256 755 700 700, for immediate help.
travel.stackexchange.com/users/1694/Noah Kiganda
It's true; Uganda, Rwanda and DRC both have Mountain Gorillas, however safety in DRC is truly not reliable unlike in Uganda and Rwanda.
So on the scoreboard of safety DRC scores least.
When it comes to price, a gorilla permit (a must have in both Uganda and Rwanda to see the mountain Gorillas) is $1500 and $600 in Rwanda and Uganda respectively.
The Ugandan Gorilla permit is way cheaper than that of Rwanda.
So on the scoreboard of price Uganda ranks best (eliminating DRC because of safety).
When it comes to facilities and service Uganda ranks equally as good as Rwanda.
So you would spend twice in Rwanda than in Uganda for the same experience and quality of service.
travel.stackexchange.com/users/88282/Mathy005
Now, in the year 2017, Uganda has the best value for the price.
I did Gorilla Tracking in Bwindi National Park in August 2017 for 600 USD per person.
It was well organized with good rangers.
The walk was unexpected easy and short, but depends on the place and the family you visit.
It was possible to book the day before (with some luck).
Rwanda charges 1500 USD per person since this year.
Way too much.
Congo charges 400 USD afaik.
But is much less safe and more complicated.
This year, three rangers have been shot in the Virungas by rebels.
But: I wouldn't do it one more time,
no matter where.
It is to much money for just a few hours in the forrest and one hour with the Gorillas.
travel.stackexchange.com/users/26975/this.myself
I understand that you can see gorillas in the wild in Uganda, Rwanda and Congo. In planning a trip to Africa to see gorillas, why might I choose one country over another considering factors such as safety, price, conservation practices and likelihood of seeing gorillas?
Which country should I go to in order to see gorillas?
travel.stackexchange.com
<safety><nature-and-wildlife><uganda>
travel.stackexchange.com/questions/1454
travel.stackexchange.com/users/155/g .
Uganda, Rwanda and DRC all have Mountain Gorillas, however safety in DRC is truly not reliable unlike in Uganda and Rwanda. A gorilla permit necessary to see one costs $1500 and $600 in Rwanda and Uganda respectively, and the facilities and service are comparable in boh countries. Firstly, safety in DRC is worse compared to Uganda and Rawanda. Secondly, a gorilla permit costs between 1500 dollars and 600 dollars in both Rwanda and Uganda  where  the ranking of  servie and facilites is also equal. However , you are more likely to spot Gorillas in Uganda.
You are more likely to see Gorillas in Uganada than anywhere else. Firstly, Safety in DRC is worse compared to Uganda and Rawanda. Secondly, a gorilla permit costs between 1500 dollars and 600 dollars in both Rwanda and Uganda  where  the ranking of  servie and facilites is also equal.