If these programs were integrated between each other, there would be less room for error.  If you change an address in one program, it should reflect in all profiles no matter which program (RE, GE or FE)  same for any transaction details. The fund, no matter which program you're using, should give you all the activity information, whether a gift is put in through RE or transferred from GE. This would also create more accurate query's.  You should be able to pull interfund gifts into a query created in RE to give the most accurate information for transactions/donation history.