Front teeth: connected or separate crowns? Due replacing front dental crowns (upper) (x-ray provided) (Photo)

My dentist was advising me in connected crowns for better bone support (avoid bone loss tissue), the ones I had in place until now are separate, so I've opted out for separate ones against her recommendation as I've read online if possible separate is better. I've had these for 10yrs, no problems other than the inside gum line was bit higher, suspecting this was due bad construction of crowns, material was porcelain cover/metal casing, now having done zirconia crowns (will that improve gumline?)