Attack mode 6 and 7 give vastly different speeds

[OqQCP78Bz]

Hi all,

I'm using hashcat v5.1.0 with 2x GTX980Ti's and the latest nVidia drivers on windows 10 x64

I'm trying to use a ?a modifier on the left hand side of a word list and then a right hand side of the word list however the speed difference between the two is significant as per below: 

When I use the following command for -a 6:

Code:

C:\hashcat-5.1.0>hashcat64.exe -m 1000 -a 6 NTLM.txt --username "C:\Wordlists\crackstation.txt\realuniq.lst" ?a -O -w 3

Speed.#1.........:   845.9 MH/s (32.26ms) @ Accel:128 Loops:95 Thr:1024 Vec:1

Speed.#2.........:   879.8 MH/s (31.98ms) @ Accel:128 Loops:95 Thr:1024 Vec:1
Speed.#*.........:  1688.1 MH/ss

And for -a 7 I get

Code:

C:\hashcat-5.1.0>hashcat64.exe -m 1000 -a 7 NTLM.txt --username ?a "C:\Wordlists\crackstation.txt\realuniq.lst" -O -w 3

Speed.#1.........:   212.8 MH/s (28.67ms) @ Accel:128 Loops:95 Thr:1024 Vec:1

Speed.#2.........:   226.8 MH/s (28.40ms) @ Accel:128 Loops:95 Thr:1024 Vec:1
Speed.#*.........:   439.6 MH/s

I've included the --username as the NTLM.txt file has the usernames as well. Removing the usernames from the file and dropping the --username flag doesn't seem to change anything. 

Am I missing something obvious here? How can I get the speed of -a 7 to match that of -a 6?

Thanks!