Good question, First, I am not quite sure about both of them, but:
Both (CST and RT) have one common thing - they may be applied to older adults to improve their well-being.
Reminiscence therapy is seemed to be grounded in helping elderly population to recover from depression and mood disorders which are by the way typical to some older adults because of the neurobiological mechanisms of ageing. Webster's scale [J Geront 1993] comprises developmental problems of elderly which are time management (boredom) and resolving the conflicts (see Erikson's ego integrity vs despair). The paradigm would be more humanistic
When it comes to CST - the target would be a different subgroup of individuals with progressing mental decline which is prevalent in disorders such as dementia, Alzheimer, strokes etc. The aim is to stimulate individual to activity and decrease the memory loss. CST has normally social setting so it would be performed in a group sessions. Brief description of exercises may be found in page 7 http://www.google.pl/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&sqi=2&ved=0CDIQFjAB&url=http%3A%2F%2Fwww.thecochranelibrary.com%2Fdetails%2Ffile%2F1479301%2FCD005562.html&ei=-h0rVMvYDcbJPKuxgcAJ&usg=AFQjCNFtb4aUj8kI-0L3gE7HAppSZ3uaaw&bvm=bv.76477589,d.ZWU
The paradigm would be more cognitive-behavioral here
Definetely it's not the full answer but I hope it might be helpful for others to explorate it.
While cognitive stimulation therapy, as I understand, involves targeting cognitive skills stimulation and skills training related to association, reasoning, logical thinking, working memory, long-term memory, information retrieval, etc through a a variety of activities such as discussion of topics of general knowledge, history, geography, science, etc, as well paper-pencil exercises, such as word search, word puzzle, reasoning exercise, math, etc, and computer simulated mind stimulation games, reminiscence therapy focuses on recollection of personal memory related events, ensuring primarily positive memories so as not to stimulate negative associations or agitation associated with those memories, and both have been studied with geriatric patients to demonstrate their efficacy. We have pioneered and practiced a model of mind stimulation therapy (MST) which incorporates aspects of cognitive stimulation, reminiscence therapy, body-movement-relaxation exercise, and discussion and or paper-pencil reflection on personal goals, existential perspectives in working with persons with challenging mental health populations, such as persons with schizophrenia, dual diagnosed substance abuse clients, and psychologically and physically compromised adults in nursing home. See our publications in www.psychologymentalhealth.com
Also the model is described in our recently published book: Mind Stimulation Therapy: Cognitive Intervention for Persons with Schizophrenia by Mohiuddin Ahmed and Charles Boisvert, Routledge, NY, 2013
In the book, we provide a rationale for the use of MIND as an integrative concept that is universally used by human beings across cultures, which is involved in conscious processing of information that directs our thinking, feeling, and behavior, and all that we do as part of our conscious existence. We provide scenarios in which we describe how active stimulation of the MIND can have a positive impact on adaptive thinking, feeling, and coping with one's current life circumstances and situations, de-emphasizing focusing on "deficit" aspects of the "MIND" that may be associated with long-term habits and negative feelings and associations, the focus of which may be counter-productive in working with people having long-term psychological problems and issues.