The Marianne has a substantially lower build-quality than the Grobs (poor
gluejoints, welding, design). It is uncertain how much longer Centrair will
be the tc-holder (spares availability, support, AD's), whereas LTB Lindner
has great service for the Grobs. Increase of service life is covered by SB
201-12R2, but I am unsure how this has been translated into the
FAA-approved manuals. Please note that the Marianne has a very strong
tendency to rotate to a steep attitude on winch launches due to awkward
placement (low, aft) of the CofG release.

In all: go for the sensible option and but a Twin I would say.