American billionaire Michael Eisner will address fans on Thursday with details of his £5.67m offer for 100% of the promoted League Two club.
Shareholders and PST members will vote on the former Walt Disney chief executive's proposals later this month.
"I don't think that we should think this is our only chance," Brown said.
Eisner, 75, has presented the terms of his offer before a town hall-style meeting at Portsmouth's Guildhall on Thursday.
Among his proposals are a further £10m equity investment, as well as the removal of three PST members from the club's nine-strong board.
The PST own 48% of the club after helping bring it out of administration in 2013.
Rather than instructing shareholders to vote in favour of Eisner's deal, the PST and club presidents have told fans to make up their own minds.
"What people need to do is see if it's the right option and the right person," Brown told BBC Radio Solent.
"That's the difficulty for people as you're dealing with somebody you don't know.
"Thursday is a chance for some people to look him in the eye in a public forum and ask him some questions and we'll see what he has got to say then.
"It's a huge decision about the future of the club, one that will define the path in goes on in the next few years. The beauty is that it's the fans that are making it."
Portsmouth FC and Pompey Supporters' Trust (PST) board member Ashley Brown has urged fans to make an informed choice over a proposed takeover.