IMHO... and expect that no one could jump into me by what I'm telling is... All and none.
All: Because the ones said here all have made their own name on the tracks, they do really nice products and they stay up to their product (up to some limits...).
None: Just because the same engine modded by two different tuners are quite different, sometimes they look for a higher absolute power, sometimes they look for a better mid-high rpms, sometimes... (put whatever may apply here).
In the past, modded by myself my own engines and got very good results, in fact, some people interested on them and did some for people that get quite satisfied with the overall performance of them. Actually I'm too lazy for modding my own engines and got some units from, so I can speak of them.
The one I'm speaking is Jim Hottinger (Hot Mods). Bought a Plus 21-7 for my Truggy and I'm really satisfied with the work and performance of the engine. The best of all is it doesn't carries fancy cuts and their work is very subtle except for some details. I post some photos of the work of Jim on a Nova Plus 21-7 Off-Road engine. Take into account that you will not see 'shiny' work and the images are fairly near macro shots (you could clearly see my digital imprints in some of those photos
).
Sleeve:
Crankshaft (hardcoated - stock in their package).
Crankcase
Things that a stocker doesn't have on the outside...
After some tanks and being almost finishing the break-in need to say that I really like the powerband of this engine and the overall feeling with it, strong and very linear, surely I'll repeat with more products from Jim in the future.