Some strength coaches see a good deadlift as the outcome of excellence at other disciplines, so there is no need to specifically add deadlifting itself to a solid program.
Personally I could take or leave DL, I have it in my routine right now but I sumo lift as I need to work on hamstring strength due to suffering from backpain largely due to pelvis alignment issues. The other thing to note about sumo is your lift succeeds or fails in the first inches off the ground where the power is going through your legs and your back is fixed in a "strong" position, whereas your classic deadlift stance the off the ground is the easy part and you are fighting with the weight getting upright where your back is at its most vulnerable.
First of all: A wide stance low bar back squat going down to parallel together with conventional deadlifts will strengthen your hamstrings and glutes greatly. There are reasons to pull sumo, those reasons are mainly proportion-related. Most people I've talked to who pull sumo at meets usually also train using the conventional dead lift (see for example Dan Green).
Second of all: I'm going to assume that your pelvis suffer from an anterior tilt. If so, then focus more on stretching your psoas muscles since these are usually very tight in people who sit down a lot (and you browse HNews) and pulls on your pelvis. Strengthening your back, hamstrings, glutes and quads aren't a bad idea either, it's just that these are things that usually come with a good training program.
Third of all: The position that is toughest for the lifter is largely dependent on the lifter's own weaknesses. I, for example, deadlift conventionally and have the most trouble to come off the floor because I usually do touch-and-go DLs.
Personally I could take or leave DL, I have it in my routine right now but I sumo lift as I need to work on hamstring strength due to suffering from backpain largely due to pelvis alignment issues. The other thing to note about sumo is your lift succeeds or fails in the first inches off the ground where the power is going through your legs and your back is fixed in a "strong" position, whereas your classic deadlift stance the off the ground is the easy part and you are fighting with the weight getting upright where your back is at its most vulnerable.