Does replacing outside A/C unit require replacing inside unit
I have a 10 year old 10SEER Trane outside and inside unit. The coil is leaking freon in a few spots. The first technician gave me a quote to replace the outside and inside air handler with a 13SEER for around $4800. The second technician I called came out and suggested only replacing the outside unit with a 13SEER for $2000. He told me that the new outside unit would work with the inside unit.
Out of the 8 quotes I received, only two recommended only replacing the outside unit. Is there a reason I should replace both?