Variable Content by ESP

SFMC (ExactTarget)

%%[if emailversion == "V1" then]%%
V1 CONTENT GOES HERE
%%[elseif emailversion == "V2" then]%%
V2 CONTENT GOES HERE
%%[else]%%
DEFAULT CONTENT GOES HERE
%%[endif]%%

Campaign Monitor

[if:emailversion=V1]
V1 CONTENT GOES HERE
[elseif:emailversion=V2]
V2 CONTENT GOES HERE
[else]
DEFAULT CONTENT GOES HERE
[endif]

MailChimp

*|IF:emailversion=V1|*
V1 CONTENT GOES HERE
*|ELSEIF:emailversion=V2|*
V2 CONTENT GOES HERE
*|ELSE:|*
DEFAULT CONTENT GOES HERE
*|END:IF|*