The transition to the Chez Scheme back end is almost bug compatible [1], so if it worked in the old version, it should work in the new one.
One advantage or migrating it to the Chez Scheme version is that some tricky functions (like print or display that have like a million of corner cases) are implemented in Racket or in Chez Scheme, so it's not necessary to write them again in JavaScript.
[1] For example in the old version, only the small chars were interned and in the new version all are interned, so code like (eq? #\λ (integer->char (char->integer #\λ))) may have a different result. It's true in the new version, but in the old version it may be false if the optimizer is not aggressive enough with the constant folding.
One advantage or migrating it to the Chez Scheme version is that some tricky functions (like print or display that have like a million of corner cases) are implemented in Racket or in Chez Scheme, so it's not necessary to write them again in JavaScript.
[1] For example in the old version, only the small chars were interned and in the new version all are interned, so code like (eq? #\λ (integer->char (char->integer #\λ))) may have a different result. It's true in the new version, but in the old version it may be false if the optimizer is not aggressive enough with the constant folding.