Not having kids for hopefully 10+ years from now, but I love both of these names. I have a problem though; I’d definitely use [name_f]Winnie[/name_f]/[name_u]Wynn[/name_u] and [name_f]Gwen[/name_f]/[name_f]Gwennie[/name_f] for nicknames and I hate rhymey names. So that means I have to chose. My taste in names might change in a decade, but I want to hear others opinions on the names, or what you would chose in a situation like this! [name_m]Just[/name_m] curious 
I would go for [name_f]Winifred[/name_f]! [name_f]Winnie[/name_f]/[name_u]Wynn[/name_u] is very cute, and makes me think of [name_m]Tuck[/name_m] Everlasting.
I really like both
I love [name_f]Gwendolen[/name_f] but [name_f]Winifred[/name_f] is special; she gets my vote.
[name_f]Gwendolyn[/name_f]!
My favorite out of the two has to be [name_f]Winifred[/name_f], if only for the nickname [name_f]Winnie[/name_f]. 
Also, quick question, have you thought about a possible alternative to [name_f]Gwen[/name_f]/[name_f]Gwennie[/name_f] as a nickname for [name_f]Gwendolyn[/name_f]? Such as [name_f]Wendy[/name_f]? Or perhaps another name like [name_f]Gwendolyn[/name_f] could be used alongside [name_f]Winifred[/name_f], such as [name_f]Gwyneira[/name_f] or Gwenllian. Then you could “have your cake and eat it too.” ^^