Lens buying becomes confusing when it begins with products. It becomes clearer when it begins with where you stand, how much scene you need and whether the subject moves.
What is wrong with the current picture?
Can you not fit the room, reach the dog, focus close enough or keep the shutter fast in poor light? Each problem points towards a different lens.
Focal length changes framing and working distance
A wider lens includes more from the same position. A longer lens narrows the view. Perspective changes when the photographer moves.
Maximum aperture changes light and depth
A wider maximum aperture can allow faster shutter speeds and shallower depth, but usually adds size, weight and cost.
Prime or zoom?
A prime can be smaller or brighter. A zoom offers several framings and is often more practical for dogs, travel and changing situations.
A lens is useful when it changes which photographs are realistically available.
Use the lens you own as evidence
Review recent photographs. Which focal lengths did you use? Which failed because you could not go wider, longer, closer or brighter?
Buy from evidence
Rent, borrow or buy used when possible. A week of real photographs teaches more than a month of specification comparison.