I wouldn't say they are ideal for a beginner, if you have a choice of a 250 or 200 then go for that.
OK they are not as powerful as an MX bike obviously, but for a novice at the end of a days trialling they will be pulling you all over in the sections.
I've seen it a lot on here.....beginner buys 2.9/300/raga etc. then tries allsorts to soften them off.
What bobtlr said above, really.
I would prefer a modern bike to learn on, but twinshock riding makes you think more about your choice of line in a section, and i think, makes you a better all round rider in the long term.