Well Crudo's - yes you are right, but it goes much deeper than that.
As an example, lets use 6 meters first.
6 meters - is more ground following - like 10 / 11 meters - CB radio than 2 meters.
This means that the signal stays closer to the ground and will go up over one hill and down over the other side, and it acts a little more like HF than VHF.
Problems with 6 meters -
Anything on the tower, 9 feet long, or multiples of 9 feet acts like a radiator - antenna, and messes up the radiation pattern of the antenna.
With 6 meters it is very important that everything on the tower is tight, no loose guy wires, grounds etc.
When the band opens up, signals from hundreds and even thousands of miles away drifts in.
When it storms, the band gets so noisy, you can't hardly hear anything with your transceiver.
The antenna is large, but doesn't have to be at the top of the tower to work, which means that someone has to climb the tower to put up the antenna, and maintain the antenna system.
The duplexers used to separate the transmit signal from the received signal are very large - 6 feet tall - looks a lot like hot water heaters than the little coffee pots used for 70 cm - 440 MHz.
You wouldn't be able to lug this type of a repeater up to the top of a mountain and just put it up on a moments notice - you would have to build it and maintain it in advance.
You would have to get a coordinated pair of frequencies that wouldn't interfere with another coordinated repeater elsewhere. Which is hard to do.
And you would need a link frequency above 220 Mhz that you could use to control the repeater - since it would be illegal to put up a repeater and then just walk away from it.
2 meters -
Two meters requires the use of a better antenna - a station master antenna is in the neighborhood of about $1100.00
You have to use hardline - not coax. Very expensive, both for the hardline and the connectors.
You have to pay to get tower space or build your own tower.
You need to have the antenna as high as you can possibly get it.
The duplexers are very expensive - because everyone is looking for a good set - used, so there is very little good used equipment for sale at a reasonable price.
You have to find a pair of frequencies that you can use that is not already in use and you have to get them coordinated. No use building a repeater for 146.940 Mhz if there is already another repeater within 120 miles of your location.
Its not very easy to change the length of the coax jumpers for the duplexers or retune the antenna - good antennas are usually purpose built frequency designed from the factory to have a low VSWR.
2 meters is hard to use Solar Power just due to the amount of equipment available - most hams has some type of 2m equipment and you can only get so many watts of power per a day out of a solar panel. Which means you would either have to reduce transmit power - which would bring complaints from the users when their handheld can't transmit and receive it's signal.
You would have tower rent to pay every month - before TSHTF and you would need access to the tower site after TSHTF.
You would need a coordinated link frequency above 220 Mhz and you would probably have to join the repeater council to ensure that your coordinated frequency pair isn't stolen from you and given to someone that is friends with the people that runs the repeater council.
Its a PITB!
70 CM -
70 CM - ( 440 Mhz) by nature is much easier to get a coordinated pair, just due to the fact that the repeater usually only has a service contour area of about 60 miles - 30 miles in any direction from the base of the tower for the repeater.
The path loss is greater than 2 meters and is dependent upon time of year, since the leaves on the trees can block reliable reception.
You need a very good tower location and you need to get the antenna as high up or at the top of the tower if possible.
You would need a link frequency above 70 CM or below 70 CM - since cross talk between the link and the repeater would mess up the link and you could loose control of the repeater.
Here a dedicated phone line - copper, unpublished telephone number works well.
This also gives you the ability to have a phone patch connected to the repeater...
With 70 CM - using hardline is a must!
I have participated with some prepper groups that thought that all they needed to do to establish a repeater was tie two handheld radios together, put them in a tool box, run a piece of coax up the side of the tower, and put up their own rogue antenna on the tower and a solar panel or two on the fence to charge the handheld batteries.
The problem with trying to do something like this is that you have no way of controlling it and the loss in the feed line negates any gains you get from putting the antenna up in the air higher with coax.
Not having a coordinated pair and the repeater not being able to identify itself every 10 minutes is what gets you in trouble.
Sooner or later, someone will come along, discover it, destroy it and then you loose what ever you thought you would gain by putting up your own rogue repeater...
Some tower owners will get upset if they visit their tower and find an uninvited guest occupying space on their tower, interfering with their legal communications...
Anyway you look at it - building a repeater is not cheap, maintaining a repeater is very expensive, and owning a repeater can be a PITB...
Anytime your repeater breaks, the users expects you to drop everything and run up to the repeater site and fix it as soon as possible.
And if the repeater runs away - gets stuck in transmit or has a unauthorized user that is breaking the rules as per the Part 97 - you, not the person breaking the rules is responsible for the content on your repeater. So basically other people can get you into trouble for acting up on your repeater, and your repeater itself can cause problems for which you are responsible.
At least when you talk simplex, the only person you are responsible for is you!
