They probably are, I haven't handled a Beauforte but a quick search reveals that Carronite have a longer guarantee and the acylic used is thicker, 10 instead of 5mm. From what I can tell both are reinforced with GRP, I have a Carronite at home at it is extremely solid.
Both are great baths. Bath bath are simlar in style and look. Beaufort baths are deeper than Carron baths. Carron are made in Scotland, Beaufort made in Yorkshire. Both have a 30 year Guarantee on the reinforced versions. Both appear to be as strong as each other.
All down to price (beaufort seem to be a better pruice than Carron) and if you want a slightly deeper bath etc.