Both of these are female-centric dramas about women from different walks of life who come together and work towards a certain goal and become friends along the way. Both are also comedic with serious elements. If you like one of these it is very likely you will enjoy the other.

Both dramas tell the story through reminiscing into the characters college days.

Both have nice groups of mostly male friends surrounding a couple of females.

Both have family elements.

Both dramas have piles of delicious food.

I'm calling Lets Eat 3 Reply 2004.

These two dramas are written by the same team so there are quite a few similarities:

Slice of life rom-coms with a similar feel
Characters - two male love interests older lone tsundere who has had a career change for some reason and a younger kind love interest with a team of friends,weird/lazy boss, a funny co-worker, and an outspoken best friend
Comedic elements - running jokes assorted forms of humor

Differences: setting/careers and interests are different - in Drinking Solo they are Teachers interested in Drinking and in A Poem a Day they are medical therapists interested in Poetry.

Both feature three males attempting to lose their virginity - only one of which has a steady girl friend.

Both have pretty similar humor

Characters in Explicit Innocence are a year younger (finishing high school) than those in Twenty but they are around the same level of maturity and state of attempting figuring out their lives.

Both series are food centric rom-coms with a similar feel. Whilst Lets Eat is more about the delicious food porn Oh My Ghost is set in a restaurant so there is always food around.

Each series features an unknown food blogger element.

Both of these series also include mystery and darker storylines alongside a cute romance.