Upgrade to new OS or not

Hello all - I am somewhat of a novice, so please forgive me if my questions seem redundant or stupid.

I have a mid 2009 MacBook Pro, 2.8 GHz Intel Core 2 Duo Processor, 4GB memory. I currently have Mountain Lion installed. I have almost nothing saved on my hard-drive and very few apps installed. I have recently had to have my computer completely reinstalled on two occasions after upgrading the OS. On both occasions, the machine simply froze and I could do nothing with it. When I took it in to the Apple Store, each time was that the machine would require a complete "reformat" of the hard-drive and setting it up as a new machine. Each time I've been told "better to stick with Mountain Lion". However, I have now have no photo apps on the machine except for "photo booth". I used to use iPhoto and Aperture 2. I now have nothing. Aperture was purchased as a dvd from the apple store when I purchased the machine. The dvd is now no longer functional.

My questions are:

1. Is there any advantage to upgrading to another OS? If so, which one?

2. Which photograph package should could I use?

Thank you in anticipation of your responses and advice.