Clojurians Log v2

I have a question related to the java jdbc reducible query (with a little sql/rdb, if I should ask elsewhere let me know) If I use jdbc/reducible-query in these ways

;; version 1 (uses doseq while implicitly handling a transaction)

(jdbc/with-db-transaction [tx connection]
  (doseq [batch (jdbc/reducible-query tx sql {:fetch-size 10000})]
    (write-batch (process-batch batch))))

;; version 2 (transduces from one table to another implicitly handling a transaction)

(jdbc/with-db-transaction [tx connection]
  (transduce
   (comp (partition-all 1000)
         (map process-batch)
         (map write-batch))
   (constantly nil)
   nil
   (jdbc/reducible-query tx sql {:fetch-size 10000})))

;; version 3 (uses doseq without explicitly closing a transaction)

(jdbc/with-db-connection [conn connection]
  (.setAutoCommit (jdbc/get-connection conn) false)
  (doseq [batch (jdbc/reducible-query conn sql {:fetch-size 10000})]
    (write-batch (process-batch batch))))

;; version 4 (transduces from one table to another without explicitly closing a transaction)

(jdbc/with-db-connection [conn connection]
  (.setAutoCommit (jdbc/get-connection conn) false)
  (transduce
   (comp (partition-all 1000)
         (map process-batch)
         (map write-batch))
   (constantly nil)
   nil
   (jdbc/reducible-query conn sql {:fetch-size 10000})))

Questions 1. What are the subtle differences? 2. What are the differences if an error were to occur?