Experts such as FE Alpha Manager Giles Hargreave have suggested that the change could see a surge of new money into the market, potentially leading to a re-rating.
However, it remains highly volatile and has notably underperformed strong UK markets in recent years, raising the question of whether it is worth the bother.
Data from FE Analytics shows that the market has made just 7.57 per cent over three years, in which time the FTSE Small Cap (ex IT) has made 68.51 per cent and even the FTSE 100 has made 37.12 per cent.
Performance of indices over 3yrs
Source: FE Analytics
However, Richard Power (pictured), manager of the CFIC Octopus UK Micro Cap Growth fund, explains that stockpicking is vital in this area and that investors should not think of the market as an index.
AIM, which is designed to be easy for new companies to float into, tends to fill up with firms in certain fashionable sectors, which means it can underperform if those sectors do. "While it is true to say that the FTSE AIM All-Share Index as a whole has not done all that well in recent years, this is largely a result of AIM's natural exposure to the latest investment fashions and the significant proportion of natural resources companies that have dominated it of late."
"However, it's important to understand the market is not an index. AIM is home to a hugely diverse range of companies and it has a great many success stories – businesses that have been growing their earnings year-on-year for years and years."
"Earnings growth is the key factor behind long-term performance for a company of any size and smaller businesses have much more potential to achieve it than their larger counterparts."
Power says that careful analysis is vital to making money in the market, which houses many companies that ultimately fail.
"AIM is also a market that truly rewards expertise, as fewer analysts combined with a wide range of options means a specialist team with experience in this area has the scope to outperform significantly."
Power’s £14.5m fund takes a bespoke benchmark split equally between the FTSE Small Cap Index and AIM, and data from FE Analytics shows that it has outperformed that marker over the past three years.
The fund has made 54.89 per cent as the benchmark has made just 46.43 per cent.
Performance of fund vs benchmark over 3yrs
Source: FE Analytics
Powers says that two stocks he likes on the index are RWS Holdings and Prezzo. Both are examples that show AIM is not only a home for fledgling businesses, but that many established companies choose to remain listed there.
RWS Holdings is a patent translation and search company that helps technology and pharmaceutical companies protect their intellectual property.
Prezzo is an Italian restaurant chain that first listed on AIM in March 2002.
"Both these companies have delivered consistent earnings growth over the last circa 10 years since they listed on AIM," Power said.
Power points out that most AIM shares also attract Business Property Relief when held for more than two years, which means that inheritance tax does not apply.
Paul Mumford, who runs the £20.6m Cavendish AIM fund, warns that there is already plenty of money in the AIM market, particularly chasing the shares that receive IHT relief.
"I think investors should be wary because a lot of AIM stocks which are IHT relief-qualifying are far too expensive," he said.
Mumford’s fund has also managed to outperform its benchmark and the AIM market over the past three years, returning 36.33 per cent against the market’s 7.57 per cent, according to data from FE Analytics.
Performance of fund vs benchmark over 3yrs
Source: FE Analytics
He says it is important to be highly selective when investing in the market and says he avoids companies with overseas earnings as well as those that look overvalued.
The oil and gas sector is one of the most interesting for those looking for stocks to put in their ISA, he explains.
"One company I am putting money into today is Ithaca," he said. "It’s got the advantage of trading on 1x next year’s cash-flow."
"It has just taken over Valiant, so potentially there’s some gearing to it. It drills appraisal wells, not just exploration wells. It operates a low-risk strategy."
"The other one decent stock for a punter to put in their ISA would be Faroe Petroleum, which has got the advantage of net cash on the balance sheet."
Mumford says that the company benefits from doing a lot of its drilling in the Norwegian part of the North Sea, where drilling costs are reimbursed by the government.
Faroe sells on its finds to major companies rather than develop them itself, Mumford explains.
He admits that there are risks to investing in oil companies, however, chiefly that the oil price will fall.
"It’s a high-risk area, but it’s one of the sectors in the market that is quite interesting," he said.
Cavendish AIM requires a £2,500 minimum initial investment and has ongoing charges of 1.64 per cent.
The Octopus fund requires a minimum initial investment of £1,000 and charges 1.88 per cent.
Giles Hargreave's Marlborough UK Micro Cap Growth fund currently has around 80 per cent in AIM. It requires an initial £1,000 investment and charges 1.54 per cent.