Noone style is efficient over all time periods and, no one type of stock and no one industry specification will forever remain value or growth.

Restricting yourself to the traditional allocation universe of one investment style may affect your ability to manage risk and return at critical valuation points. 

Unfortunately, many managers will adopt the mantel of a style without having the necessary intellectual freedom to continuously reinvent and reassess value in the market place.   

Nevertheless, it is generally accepted that most investors are better off with fundamental long term earnings based investment disciplines

Value has been shown to out perform the market and all other styles over the longer term, although this depends on the start date and the classification of style comparison. 

In fact, larger companies, small caps, mid caps, growth stocks, value stocks and sector equivalents all exhibit periods of significant out and under performance as market demand moves from one area of preference to the next.  All areas of the market therefore have a relative as well as an absolute valuation.

Genuine long term growth stocks do out perform the market by a very wide margin, but not everybody is a genuine long term growth investor and not everyone buys at a reasonable price.

Diversified portfolios may benefit from a relative valuation approach, that is holding investments with different characteristics in proportion to their relative value and relative to the individual client's financial needs and risk preferences.

Portfolios can easily incorporate both growth and value components at the same time. An investment can also be both a growth and a value investment.  For example, emerging markets can have both growth and value characteristics, while growth stocks can be undervalued and stocks traditionally classified as value can be over valued..

Value styles tend to be lower risk because they invest in companies and areas which are  under valued and where much of the risk has already occurred. 

Although, areas which have seen large falls and poor performance are not always viewed as low risk by the average investor.

Value stocks, because their prices are depressed also tend to provide a higher level of dividends than growth investments and as such are often considered more suitable for investors who need a higher level of income from their portfolio.

Growth portfolios tend to be more aggressive in that the value of the underlying stocks are more sensitive to changes in earnings and they provide a much lower yield because prices are placing greater emphasis on future earnings than current earnings.  They are therefore generally considered more appropriate for investors with no financial demands on their portfolio and more aggressive return objectives who can afford to take a longer term investment view.

But, if you take a total return approach to investment, there is no real reason why a properly run, well disciplined, growth portfolio should be inappropriate for an investor who relies on their portfolio for income.  What it will mean is that more of the portfolio will need to be in higher yielding lower risk, fixed income investments and less of the portfolio in equities..  

As far as individuals with no financial demands on their portfolios, the value and growth universe is sufficiently large as to be able to incorporate investments with different style characteristics and still achieve a well disciplined, well balanced management of risk and return.