The Pentek US-1500 reduces asbestos but the Culligan US-EZ-4 does not. The Culligan US-EZ-4 reduces chloramines but the Pentek US-1500 filters do not.
You are correct, the replacement filters for the Culligan US-EZ-4 only work with the Culligan US-EZ-4. Whereas, the filters for the Pentek US-1500 can be used in many other filter housings for 10" slimline filters. You can also use several other filters in the Pentek US-1500 system. For example, you could purchase the Culligan D-40 and the Culligan D-28 filter to use instead of the P-250 replacement filter. The D-28 also reduces chloramines so you could get choramine reduction there as well.
The Pentek US-1500 has a better electronic monitor as well. The Culligan US-EZ-4 monitor monitors time whereas the Pentek US-1500 monitors usage.
The Culligan US-EZ-4 has an easy to change filter. You simply screw off the old filter and screw on the new filter. The Pentek US-1500 has the filter housings that you have to screw off first. A wrench does come with the system to assist in removing the housings.
I hope this helps. Here are some of the products mentioned in this post:
Pentek US-1500 Water Filter System with Electric Monitor and Pentek US1500 Under Sink Drinking Water Pentek P-250A replacement filters and Pentek P250A under sink water filters Culligan US-EZ-4 UnderSink Drinking Water Filter and Culligan USEZ4 Under Sink Filter 01019054 Culligan RC-EZ-4 Water Filter Cartridge and Culligan RCEZ4 Replacement Filters 01019057 Culligan D-40 replacement filter and Culligan D40 under sink water filter Culligan D-28 Chloramines Reduction Water Filter and Culligan D28 Replacement Filter for Chloramine Filtration