The DE89 is a mild, straight bar razor. I have one and can get great shaves with it.
The Slant has the blade twisted slightly, which stiffens the blade. They are efficient shavers. I have been taking a break from my Merkur 37C slant after using it for a month. I never did get a shave with no weepers with the Slant. I used my Mission and had a blood-free shave, then I used my DE89 and got 2 BBS shaves in a row.
Since I last posted, I've bought 3 shave sticks (La Toja, Speick, and Palmolive) and 2 vintage Gillettes (and Old-type, and a New-type long comb). The Old gave me a near BBS shave on the first try. The New did not give me a great shave, but I didn't prep as much as usual either.
I do NOT like the old Gillette ball-end handles! They are a hollow brass tube with the ball-end and screw-end pressed into the ends of the tube. Luckily my DE89 and Mission handles fit the Old and New Gillettes.