One consideration might be with function. Would you like it to function like a full-size firearm, or would you prefer it to have a different manual of arms? I prefer that the training rifle work as exactly as possible to the full-size firearm. The Crickett and the Henry require the user to #### the striker as a separate step (presumably for 'safety'); the Rascal - on the other hand - works just like your rifle. The Crickett also comes with an extra, buit-in, lock-out device (presumably for 'safety'); it's easily activated - even by accident - but you need an Ace-type key to unlock it. Another consideration might be with the rifle's size, weight, trigger weight, and and length-of-pull. The Rascal, at ~10.5" LOP, fits kids who wouldn't be able to use a rifle with a longer LOP. The Rascal's Accutrigger enables a trigger pull that matches a full-size rifle, rather than being artificially heavy (presumably for 'safety'), as are the triggers on some of the other options.
With regard to the wood vs. synthetic (and blued vs, stainless) question, I'll ask you this: "When should a youth learn to care for his/her firearm?" There's no better time than the present, I think. The increased care demanded by wood and blued carbon steel will teach the youth lessons that he/she needs to learn. Having learned those lessons early, he'll/she'll take those (valuable) experiences with him/her as he/she grows.
All that said, I think that the 10.5" LOP, walnut-stocked Savage Rascal is probably the single best off-the-shelf option for the very smallest shooters.
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