Depends. If the system has great VTT support, I like the extra crunch. I'm not sure I would be running Warhammer Fantasy RPG 4e (WFRP4e) if it were not for the excellent Foundry system and modules Cubicle 7 sells.
Also, it depends on how streamlines and well presented the rules are. If I have to do a lot of page flipping, study the rules like a preparing a research paper, and creating my own in-game cheat sheets to run it--blech! WFRP4e is pretty bad in this regard. I feel the rules are spread throughout the core book in a way that makes it difficult to easily learn and reference. The rules are well designed, and easy to pick up in play as a player if the GM is very familiar with the rules. But I feel like I'm having to jump around the rules and having to reread thing multiple times to "get it." Also their additional books improve and fix some of the rough edges of certain areas, such as how Magic works, but then I have to reference multiple books.
Luckily having all the content in a VTT, with everything cross referenced and searchable, and having a lot of the crunch automated by the character sheet, chat commands, etc. makes it much more manageable.
Similarly, I'm loving how the crunchy combat in Crucible is developing. But it is developed specifically for Foundry by the Foundry developers, so tracking all the various advantages, disadvantages, conditions, etc. are done by the VTT making it very easy to run. But I would never want to run that system in a pen and paper game.
On the other hand, DCC is a game that is not particularly "crunchy" but the need to constantly reference and roll on tables (which includes for every spell) led me to decide not to run it. The core system has good VTT support, which automates most of the table rolls, but I backed the Kickstarter for, and was hoping to run, Dying Earth, and the new classes are not yet supported in Foundry or Fantasy Grounds. Running it as a pen and paper game, especially for magic user players seems like it would require torturously long turns of not just spell selection but flipping pages to look up and roll on tables.
For pen and paper, DnD 5e is about as crunchy as I would want to get.