It depends on your current 401k plan. If there are no "inactive account fees" or anything like that, and you have access to good funds, then it's perfectly reasonable to keep it where it is.
Generally, rolling to a traditional IRA is your best plan. You can always do more gradual Roth conversions, so you don't take the tax hit all at once if you want to go that route.
This. Don't think about A
or B. It's not an all or nothing proposal.
If you estimate that your retirement tax bracket is going to be higher than your current tax bracket... you convert some amount up to the top of your tax bracket.
But.. if you're in the 28% bracket now... it is also somewhat likely that you'll be in a lower bracket later. If that's the case, it makes sense to just let it bake in the traditional IRA, then start converting when you slide down one or two brackets in retirement.
There is, of course, the whole "you can't pull it out for 5 years" clause on the conversion. So, if you "convert later" you'll also need to have some forethought in how you'll finance that first 5 years.