use redweb, better recognition by police. Redweb has been tried in court, bouncer hasn't.
Cant remember where i read it but there is a fantastic letter on the net from a legal person. Talked about all 3 forms, dyes, smells, and harmful. Dyes are legal, smells has not been tried in court so are 50/50 (i think they should be legal...great for getting people out of a toilet cubical) and harmful like OC and stuff which are illegal.
Ultimatly, redweb is the only one recognised by ACPO, you have to be trained and registered to use it. Plus its the most effective (in my opinion)