I would generally agree with Irlandesa's assessment. It's probably a mostly a lateral move, maybe a slight improvement. I would think that, at present, Hallmark is the slightly higher setting.
Lifetime gained quite a reputation for women in peril stories dating back to the 90s. My friends and I used to jokingly refer to it as the Women in Jeopardy Channel. I legitimately wondered how the network would fair with the advent of keyless entry since women dropping their car keys as they ran to escape was such a trope for them.
At its peak, Lifetime tended to cast primetime actors and actresses, mostly from primetime soaps such as 90210 and Melrose Place and the like and 90s teen stars transitioning to adulthood. Tori Spelling had quite a run for a time. (For reals, Mother May I Sleep With Danger is a legit touchstone for women of my generation. If you ever come across it, I recommend it for the truly glorious ridiculousness of it.) They've tried to change their image with some non-stalker themed series. And they are sometimes not bad. But the movies are still ludicrous and at this point it seem to be mostly filled soap actors trying to get a foothold and former primetime actors.
Hallmark favors paint by numbers rom-coms and cheeky upbeat mystery series. Hallmark seems to have a stable of actors and churns out hundreds of movies a year, particularly holiday films. The actors seem to be a combination of former daytime and primetime actors of limited notariety and a slew of Canadian actors who also appear in SyFy channel shows (yeah, I watch too much TV). They are legitimately charming, however, and are better received than the Lifetime stuff. And once you get in with them, the work appears to be consistent.