I only use the arpeggiator on the OB6 for very simple rhythm stuff.
For the majority of my arp and Seq needs, I use my Arturia gear:
Minibrute 2S
Beatstep Pro
Keystep
The Minibrute has four tracks in the sequencer so you can do duo-phonic with gate or monophonic with 2 mods (i.e. a monosynth with pitch, gate, MOD1, MOD2) and record it live or step program with knobs for every step (up to 64 steps)...also has a sophisticated arp
The Beatstep has two monosynth tracks with pitch, gate, velocity in addition to the full drum sequencer (both 64 steps, drum has 16 assignable pads...I use soft-synths or my Roland SoundCanvas
The Keystep has 8-note poly sequencing capability also 64 steps, this is my main unit for programming the OB-6 seq. It also has a fairly sophisticated set of live tools for arp, play-along, chord morphing, etc...
All the Arturia boxes have a background app with a reasonable (better than Soundtower for sure) editor for the sequences.
I bought all three used for a total of $600...considering my investment in the OB-6 this is a big performance multiplier