The difference, Mehmet, is that the UN troops had no mandate to use force to guarrantee the peace and the British were little interested in the strife outside their sovereign territory but EU would have interest to protect all EU states and treat all EU citizens equally. The same cannot be said of Turkey.
the issue isn't so much whether there are bases but whether they have responsibility for security.
And for whom security?
The presence of Turkish troops on Cyprus soil would undermine Cypriot reconciliation and brotherhood by creating an environment of distrust between GC's and TC's. It would help pave the way for more Turkish colonists in Cyprus. The troops and colonists would represent the interests of Turkey by "Turkifying" Cyprus. Does that make you feel safe and secure? Does it leave you optimistic about prospects of reconciliation?
By contrast, if northern Cyprus joined southern Cyprus in the EU, the whole island would have the advantages of EU membership, including security. Aggression in Cyprus would be aggression in the EU! EU troops in Cyprus would provide better security for everyone, GC and TC, and their presence be better news for peace, reconciliation and the functionality of any settlement.
Any paper "agreement" that is not supported by all parties and lacks guarrantees and incentives will as workable as the 1960 Cyprus Independence or the 1938 Anglo-German peace agreement.