If you intend to do mostly landscape and maybe T1 stuffs you can enjoy both of them but if you wants to do more than that I suggest you to park the LM and focus on Cappy (save your time and ofc. real money!)
Cappy is like an "upgraded heavy armored LM" that can support, dps, use pets, tank and heal much better.
With Cappy you will have no problem at all to play any end game content, on the contrary -> this is the most wanted class for any 3/3, 6/6 and ofc. the raid.
Now that support is not really needed at end game, most of the players see LM's as a leech that hold and slow them down.
Some instance are excluded/very hard for LM's (like filth-well) and many players prefer in advance not to join/take LM's while Cappy's are the best class to take there.
Only one LM can be in raid but Cappy can be even more than 2 so you will have less competition to join for a raid.
Also, Cappy is well updated class while LM's are one of the most dated ones that dev's are constantly ignore any community feedbacks.
I hope I help you
