Is this an issue with deep matching/object identity?

AssertionError: expected <BN: 204fce5e3e25026110000000> to equal <BN: 204fce5e3e25026110000000>

It seems strange that chai.should seems to work fine with the same vars:

// works
supplyCap.should.be.bignumber.equal(_cap);
      
// doesn't work
assert.equal(supplyCap, _cap);