power - Individual Three Phase Potential Transformers vs Three Potential Transformers in one case

If I had to select between Individual Three Phase Potential Transformers vs Three Potential Transformers in one case for a 600V system (which doesn't require many inches of spacing between phases to avoid arcing). I know the later saves space and about 15% of money. But, should I worry about mutual inductance, mutual interference? The interference I'm referring to, is measuring in one phase also contributions from the other phases to it, instead of the accurate voltage present in that phase alone. Also there seems to be Three Potential Transformers in one case which share a common core and those which are basically individual PTs glued together. Any difference from interference point of view? Is there any bigger inaccuracy in readings in having open delta PTs vs 3 winding PTs?