anyone can tell me the advantages of one over another? thanks

This would be best asked in the Classic & Vintage forum. My quick reply, a welded frame will be lighter, (a few ounces) a lugged frame will look better (personal opinion). I have never ridden a welded steel frame so I can't give you imput about the quality of the ride but I am pretty certain there will be good and bad just like all frame materials and fabrication techniques.

thanks, I believe it makes sense. I tried a few Al welded frames, put the same wheels and seat just to compare 'apples to apples' and noticed the difference - more harsh and less comfortable ride
I suppose high end Al is ok, but few ounces difference is not important to me
i'll try to find more info where you recommended