I have no experience with the MacDonald set but I have used the Veritas/Lee Valley plunger and edge guide for various uses, mostly excavating for 1/16" thick banding and marquetry inlays. I've found them easy to learn and use. A center kit attachment for circular/oval guides also comes with the edge guide. I have not used it as of yet but I know some who have and reported that it was efficient and produced what was hoped. I have no experience with the newly released (for me) traveler or task light attachments. However, I do have the precision adjuster, which is extremely useful.
I've had no problems with either plunger and edge guide. The plunger has a locking mechanism and depth guide that helps a lot. The edge guide has optional 12" rods that can extend the length from the edge to about a foot. I found the instructions worthwhile. If you haven't already done so, I'd suggest downloading the plunger and edge guide instructions at http://www.leevalley.com/en/wood/Page.aspx?p=73720&cat=1,260,43000,51208,73720 for better insights and expectations.
Of course, for either product set, it would be wise to score the edge before excavating. That being said, I forgot one time but luckily had no tear out.