The OSTC2n is a very well made piece of hardware - it costs around half the price of comparable computers, some of which do not offer anything close to the same level of functionality or customisation.
You are able very easily to completely replace the software/firmware in the computer as new functionality is created for it, and there is an active community involved in improving/testing/helping anyone who has one of these computers.
If you have the technical skills and ability, you are able to completely replace the software/firmware with something you have written yourself, or you can customise the supplied software if you wish - all the information about the internal design (electronics) of the computer, all the program code for the software/firmware is freely available and there are many people who are willing to give help and advice at any level to a new user.
I do not know of any other dive computer that you can have such wide access to.
Even if you just buy one and use it with the supplied (and installed) firmware/software it is half the price of it's competitors, very well made, and offers comprehensive functionality.
For me it was an easy decision, and my only regret is that I didn't buy one sooner
Best wishes