Being on hold at Bristol is fairly normal - most Universities do this and then will make gradual offers after January, but unlike Bristol, they just don't tell you.
York and Durham are very different Uni environments. In terms of academics and impact on your future career, neither will give you any significant advantage over the other. However, some people find the Durham college system, and the attitudes of some of the more privileged students, irritating. If you want to study amongst a more diverse student population, and at a more conventional University, York might suit you better - and York doesn't use LNAT.