They use the same action, but there are significant differences.
They come with many different options in stock design, but any aftermarket stock made for one will fit the other. You may have to make small alterations to a stock made for a Weatherby if you put it on the Howa because of the different safety design. Or for different barrel contours.
I "think" the new S2 Vangurd has a 3 position safety, but I know older Vanguards had a 2 position safety and all Howa's have a 3 position safety.
The Vanguard uses a 24" barrel on standard chamberings and 26" on magnums. The Howa barrels are 2" shorter. Both offer 20" carbine versions. I believe Howa offers more options for some specialized models with heavy target barrels where the Vanguard is primarily geared as a hunting rifle.
The Vanguard uses a fluted bolt, the Howa is smooth.
The Vangurd used a serrated trigger, the Howa is smooth
I've owned 3-4 Vanguards and 2 Howa's over the years. I've found the Howa to be slightly more expensive and to be slightly more accurate and with better triggers. I know that is a small example, but those are my observations.
They are decent guns that tend to shoot well enough. I no longer have any of them, I simply had better guns that better suited my tastes and needs. But I'd recommend either for someone looking for a quality gun at a good price.
It shouldn't be problem for your intended purposes, but the biggest negative to either is their weight. They are the heavest of all common rifles in production today. The main reason I sold mine was because I had rifles that weighed up to 3 lbs less, that were more accurate. Not that they were inaccurate, just not up to other rifles I owned.
