easier to splice but using your own heavier wiring+relay is better, even if all you do is stuff the whole relay and harness in a corner and use the original wiring for the relay's control circuit. Led bulb replacements are all kind of lame at this point. You'll be wasting your time if you go that route. A better route if you're set on replacing the halogens would be to do an HID conversion on them. Before you start a conversion, make sure the light housing and lens is deep enough to hold an hid bulb. Otherwise, you should just stick with the halogen because they'll blow away any retrofit h3 led bulb anyways..
As a side bar, i just tried the Eiko brand par46 150w aircraft landing spots just to compare them to Wagner's, and the Eiko's rock too. The output is a very nice even rectangular chunk of light. no waves or funny hotspot/patterns in the beam.