Yes, water coolers are usually much easier to mount. Most air coolers that are decently effective are not just tall, they are also pretty wide, and are often hard to mount on a number of motherboards (that was the main reason I stopped using them), they don't fit due to nearby elements such as RAM, chipset heatsinks, etc. Another point is that they significantly hinder airflow inside the case (unless your case is gigantic), so that additional case fans are a lot less effective.
As far as cooling efficiency goes, you can find many, many tests online comparing various solutions. Whereas there certainly are air coolers that come close to good water coolers, and water coolers that are pretty lousy and are worse than good air coolers, I don't really remember any test not showing at least a slight benefit of water coolers for high TDP CPUs.
If you're overclocking your CPU, in my humble experience, watercooling is hard to avoid (keeping the above in mind: if you want something that is not a headache to mount/or will ruin your motherboard.) My main workstation has a Core i7-5930K @4.4GHz, and I couldn't get to this figure reliably with air coolers. Of course not saying this isn't possible - just that it's usually much harder to achieve.
Now for CPUs with moderate TDP and not overclocked, the story is different, and I would likely go for air cooling. But water cooling still has the above benefits (first paragraph.) My criterion of "moderate TDP" is under 100W.
Now don't underestimate the risks associated with water cooling. Leaking does happen, even with well known brands, but Alphacool makes IMO higher quality stuff than average. Check your installation every once in a while, especially the tubing.