As you spend time on TransgenderHeaven (TGH) and CrossdresserHeaven (CDH), you will notice some particular differences.
By my estimation, the sites split out like this:
CDH – The members are those who were assigned male at birth, but like to dress in women’s clothing and present as female. When not dressed, they typically assume traditional male roles and tend to be heterosexual and their gender identity is cis gender male. There is discussion aimed at clothing, makeup, going out in public when presenting as female, etc.
TGH – The members tend to be those who are questioning their gender identity or those who have essentially figured it out and are contemplating taking steps towards transitioning or have already started. There are specific sections on the physical, emotional and social aspects of transition. There is also a section dealing with how to come out. There is a makeup section, but there is no section dealing with clothing and fashion.
While the sites are not interchangeable, there is a fair amount of overlap and some are members of both sites.